Move `public/*` to `public/assets/*`

Some old PRs (like #15219) introduced inconsistent directory system.

For example: why the local directory "public" is accessed by
`http://site/assets`? How to serve the ".well-known" files properly in
the public directory?

For convention rules, the "public" directory is widely used for the
website's root directory. It shouldn't be an exception for Gitea.

So, this PR makes the things consistent:

* `http://site/assets/foo` means `{CustomPath}/public/assets/foo`.
* `{CustomPath}/public/.well-known` and `{CustomPath}/public/robots.txt`
can be used in the future.

This PR is also a prerequisite for a clear solution for:
* #21942
* #25892 
* discourse.gitea.io: [.well-known path serving custom files behind
proxy?](https://discourse.gitea.io/t/well-known-path-serving-custom-files-behind-proxy/5445/1)

This PR is breaking for users who have custom "public" files (CSS/JS).
After getting approvals, I will update the documents.

----

## ⚠️ BREAKING ⚠️

If you have files in your "custom/public/" folder, please move them to
"custom/public/assets/".

---------

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Giteabot <teabot@gitea.io>

Save another 50KB of CSS by removing unused and useless Fomantic
variants.

Removed the last instance if a `tertiary` button and fixed a TODO:

<img width="509" alt="Screenshot 2023-06-15 at 22 34 36"
src="https://github.com/go-gitea/gitea/assets/115237/8a16ae7b-2b17-439b-a096-60a52724e3d6">

Use [PDFObject](https://pdfobject.com/) to embed PDFs, replacing our
outdated PDF.js copy we vendor (the last non-webpack vendoring).

[Commit
1](673e0263da)
is the PDFObject integration
[Commit
2](9336f5769d)
is the removal of PDF.js

<img width="1251" alt="Screenshot 2023-05-27 at 09 57 52"
src="https://github.com/go-gitea/gitea/assets/115237/169ce50c-bd1d-4bb0-86e5-1710bd0400a9">
<img width="1257" alt="Screenshot 2023-05-27 at 10 12 50"
src="https://github.com/go-gitea/gitea/assets/115237/318f7ee9-fb11-4093-83e7-17475aa70629">


Fallback for unsupporting browsers (most mobile ones, except Firefox
Mobile):

<img width="358" alt="Screenshot 2023-05-27 at 09 43 34"
src="https://github.com/go-gitea/gitea/assets/115237/8c12d7ba-57d6-4228-89a0-5fef9fad0cbb">

---------

Co-authored-by: Giteabot <teabot@gitea.io>

They are not generated in some cases (although they can).

And we should keep an eye on these files when reviewing.

When reviewing, files can be marked as "Viewed" and then it is
collapsed.

Makes diffs like https://github.com/go-gitea/gitea/pull/24676/files more
readable. I'm not sure if those are actually generated, but they are
good to collapse in diffs anyways.

These files are generated using `make svg`

Running it as part of the build is really unnecessary because we have a
valid output file in the repo and assuming go dependencies do not change
unless go.mod also changes, tidy really is the best target to run the
license generation after.

Also, regenerate the file as I missed to do so during the chroma update,
and mark all json files in assets as generated.

There are a few .tmpl files outside the templates directory. Match these
as well by using `*.tmpl` glob in `.gitattributes`. Also, sort the file
alphabetically.

* Remove unused Fomantic sidebar module

The [Sidebar](https://fomantic-ui.com/modules/sidebar.html) module seems
currently unused (at least I can't find any reference to it in templates
or js), so remove it from the Fomantic build.

* remove useless minified fomantic build files

* mark fomantic build files as being generated

* Update JS dependencies and misc tweaks

- Update all JS dependencies minus webpack
- Adapt CodeMirrors styling to new CSS parent introduced by EasyMDE
- Set eslint parser to latest and add new eslint 7.14 rule
- Speed up npm install by disabling audit and fund checks
- Move fomantic-ui to optional dependencies to further speed up npm
- Enable syntax highlighting on GH for .eslintrc and .stylelintrc
- Makefile cleanups

* disable audit in npmrc

* add missing dash

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

Go templates are syntactically very similar to handlebars, this enabled
their syntax highlighting on GitHub.

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

These `linguist-vendored` attributes are only for the language stats
seen on github and they mostly haven't been updated with file
reorganizations. Move them to the two actually vendored directories.

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

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

* Exclude vendor dirs from git CRLF normalization

Should get rid of a few warnings like at the end of `lint-backend` like
https://drone.gitea.io/go-gitea/gitea/23117/1/4

* make vendor

Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

This will ensure our repo is always checked out with LF line endings
which should help Windows users who have line ending normalization
enabled.

Additionally, added the LF preference to .editorconfig.