This PR cleans up the docs in a way to make them simpler to ingest by
our [docs repo](https://gitea.com/gitea/gitea-docusaurus).

1. It includes all of the sed invocations our ingestion did, removing
the need to do it at build time.
2. It replaces the shortcode variable replacement method with
`@variable@` style, simply for easier sed invocations when required.
3. It removes unused files and moves the docs up a level as cleanup.

---------

Signed-off-by: jolheiser <john.olheiser@gmail.com>

This was intended to be a small followup for
https://github.com/go-gitea/gitea/pull/23712, but...here we are.

1. Our docs currently use `slug` as the entire URL, which makes
refactoring tricky (see https://github.com/go-gitea/gitea/pull/23712).
Instead, this PR attempts to make future refactoring easier by using
slugs as an extension of the section. (Hugo terminology)
- What the above boils down to is this PR attempts to use directory
organization as URL management. e.g. `usage/comparison.en-us.md` ->
`en-us/usage/comparison/`, `usage/packages/overview.en-us.md` ->
`en-us/usage/packages/overview/`
- Technically we could even remove `slug`, as Hugo defaults to using
filename, however at least with this PR it means `slug` only needs to be
the name for the **current file** rather than an entire URL
2. This PR adds appropriate aliases (redirects) for pages, so anything
on the internet that links to our docs should hopefully not break.
3. A minor nit I've had for a while, renaming `seek-help` to `support`.
It's a minor thing, but `seek-help` has a strange connotation to it.
4. The commits are split such that you can review the first which is the
"actual" change, and the second is added redirects so that the first
doesn't break links elsewhere.

---------

Signed-off-by: jolheiser <john.olheiser@gmail.com>

fixes a minor typo in the email templates page

- **Installation**: includes how to install Gitea and related other
tools, also includes upgrade Gitea
- **Administration**: includes how to configure Gitea, customize Gitea
and manage Gitea instance out of Gitea admin UI
- **Usage**: includes how to use Gitea's functionalities. A sub
documentation is about packages, in future we could also include CI/CD
and others.
- **Development**: includes how to integrate with Gitea's API, how to
develop new features within Gitea
- **Contributing**: includes how to contribute code to Gitea
repositories.

After this is merged, I think we can have a sub-documentation of `Usage`
part named `Actions` to describe how to use Gitea actions

---------

Co-authored-by: John Olheiser <john.olheiser@gmail.com>

This patch:
- Rename some files( `.md` to `.en-us.md`), fix missed translation copy
- Update link which shoud be refer to `../hacking-on-gitea/` instead of
`../make/` (outdated)
- Update `_redirects`:
  -  redirect `/{zh-cn|fr-fr}/make/` to `../hacking-on-gitea/`
  - redirect `/zh-cn/third-party-tools/` to `/zh-cn/integrations/`
- Delete duplicated/outdated files.
- Update menu `weight` of developers.zh-cn.md

Signed-off-by: Xinyu Zhou <i@sourcehut.net>

Add `markdownlint` linter and fix issues. Config is based on the one
from electron's repo with a few rules relaxed.

Thanks to https://github.com/go-gitea/gitea/pull/16788 I can see why our docker container kept restarting when adding the custom mail template example.
[The example template](https://docs.gitea.io/en-us/mail-templates/#example) has an error

```
2021/09/03 10:55:25 cmd/web.go:91:func1() [F] PANIC: template: mail/issue/default:35: function "AppURL" not defined
        /usr/local/go/src/html/template/template.go:374 (0x1563bb8)
        /go/src/code.gitea.io/gitea/vendor/github.com/unrolled/render/render.go:322 (0x1563782)
        /go/src/code.gitea.io/gitea/vendor/github.com/unrolled/render/render.go:202 (0x1562f8b)
        /go/src/code.gitea.io/gitea/vendor/github.com/unrolled/render/render.go:146 (0x15629d2)
        /go/src/code.gitea.io/gitea/modules/templates/base.go:88 (0x16b0769)
        /go/src/code.gitea.io/gitea/routers/web/base.go:125 (0x225f284)
        /go/src/code.gitea.io/gitea/routers/web/web.go:95 (0x2261284)
        /go/src/code.gitea.io/gitea/routers/init.go:147 (0x22817ba)
        /go/src/code.gitea.io/gitea/cmd/web.go:158 (0x239741a)
        /go/src/code.gitea.io/gitea/vendor/github.com/urfave/cli/app.go:524 (0x1740884)
        /go/src/code.gitea.io/gitea/vendor/github.com/urfave/cli/command.go:173 (0x17415f8)
        /go/src/code.gitea.io/gitea/vendor/github.com/urfave/cli/app.go:277 (0x173e8c7)
        /go/src/code.gitea.io/gitea/main.go:115 (0x23d3e69)
        /usr/local/go/src/runtime/proc.go:225 (0x443995)
        /usr/local/go/src/runtime/asm_amd64.s:1371 (0x47b360)
```

The documentation for the [fallback mail subject](d989247bb0/services/mailer/mail_issue.go (L14-L16)) was missing `{{}}` around `.Issue.Index`.

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lauris BH <lauris@nix.lv>

* Redo #13836 with new shortcode
(https://gitea.com/gitea/theme/pulls/90)

* add Api Usage

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* align "make help"

* format

* untouch build/generate-svg.js

* untouch .eslintrc

* combine editorconfig's

* rm editorconfig

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* Add template capability for issue mail subject

* Remove test string

* Fix trim subject length

* Add comment to template and run make fmt

* Add information for the template

* Rename defaultMailSubject() to fallbackMailSubject()

* General rewrite of the mail template code

* Fix .Doer name

* Use text/template for subject instead of html

* Fix subject Re: prefix

* Fix mail tests

* Fix static templates

* [skip ci] Updated translations via Crowdin

* Expose db.SetMaxOpenConns and allow non MySQL dbs to set conn pool params (#8528)

* Expose db.SetMaxOpenConns and allow other dbs to set their connection params
* Add note about port exhaustion

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>

* Prevent .code-view from overriding font on icon fonts (#8614)

* Correct some outdated statements in the contributing guidelines (#8612)

* More information for drone-cli in CONTRIBUTING.md

* Increases the version of drone-cli to 1.2.0
* Adds a note for the Docker Toolbox on Windows

Signed-off-by: LukBukkit <luk.bukkit@gmail.com>

* Fix the url for the blog repository (now on gitea.com)

Signed-off-by: LukBukkit <luk.bukkit@gmail.com>

* Remove TrN due to lack of lang context

* Redo templates to match previous code

* Fix extra character in template

* Unify PR & Issue tempaltes, fix format

* Remove default subject

* Add template tests

* Fix template

* Remove replaced function

* Provide User as models.User for better consistency

* Add docs

* Fix doc inaccuracies, improve examples

* Change mail footer to math AppName

* Add test for mail subject/body template separation

* Add support for code review comments

* Update docs/content/doc/advanced/mail-templates-us.md

Co-Authored-By: 6543 <24977596+6543@users.noreply.github.com>