* Add new JS linter rules

Adds a few useful rules from eslint-plugin-github. Notable changes:

- Forbid dataset usage, its camel-casing behaviour makes it hard to
  grep for attributes.
- Forbid .then() and .catch(), we should generally prefer await for new
  code. For rare cases where they are useful, a eslint-disable-line
  directive can be set.
- Add docs js to linting

* also enable github/array-foreach

* small tweak

Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

Currently the svg minifier (`make svg`) rewrites all `id` and `class` attributes in svg files. Every file gets the ids `a, b, ...`. If multiple svgs with ids are used on a page these ids are conflicting and the results are broken images.

| minified ids | unique ids |
| - | - |
| ![grafik](https://user-images.githubusercontent.com/1666336/132579375-59d3996f-c4e5-43b8-8c8d-82280c90d9e3.png) | ![grafik](https://user-images.githubusercontent.com/1666336/132579413-05bf9285-4e3b-4d0d-8f95-90b212405b05.png) |

This PR adds a prefix (the filename) to every id/class.

Follow up problem: Because we embed svg images there are duplicated ids if one svg image is used multiple times on a page. As those ids refer to the same content it may be no real problem because browser handle that fine.

* Update JS dependencies

- Update all JS dependencies
- Adapt to recent webpack changes
- Add new lint rules and fix issues
- Regenerate SVGs and update svgo api usage

Fixes: https://github.com/go-gitea/gitea/pull/16492

* adapt jest config and sort keys

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

* Make build scripts compatible with node 12

"fs/promises" is not in node 12, use a more compatible way to import it.
Also, lock major down versions of the image build dependencies to
prevent future surprises.

* add node_modules dependency

- Add basic frontend unit testing infrastructure using jest in ESM mode
- Rename 'make test' to 'make test-backend'
- Introduce 'make test-frontend' and 'make test' that runs both
- Bump Node.js requirement to v12. v10 will be EOL in less than a month.
- Convert all build-related JS files to ESM.

I opted to run frontend tests run as part of the compliance pipeline because
they complete fast and are not platform-specific like the golang tests.

* Update JS dependencies

- Update all JS dependencies
- For octicons, rename trashcan to trash
- For svgo, migrate to v2 api, output seems to have slightly changed but icons look the same
- For stylelint, update config, fix custom property duplicates
- For monaco, drop legacy Edge support
- For eslint, enable new rules, fix new issues
- For less-loader, remove deprecated import syntax

* update svgo usage in generate-images and rebuild logo.svg with it

- Use original gitea logo on migrate page
- Add card styles and map colors to css vars
- Tweak migrate page, adding hover effect to cards

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

* Update Octicons to v10

Besides a few renames, these icons are no longer present in v10 that we've
used, so had to change:

file-symlink-directory -> file-submodule
internal-repo -> repo
repo-force-push -> repo-push
repo-template-private -> repo-template

Fixes: https://github.com/go-gitea/gitea/issues/11889
Ref: https://github.com/primer/octicons/releases/tag/v10.0.0

* add custom sliders svg for removed octicon-settings

* apply suggestion

* fix triangles and use play on admin dashboard

* add custom mirror svg

* add missing build files

* unify custom svgs

* move to octicon-repo-clone to gitea-mirror

* use octicon-x on conflicts

* tweak timeline icons

* tweak comment buttons

* update settings icon to octicons v1

* switch to octicon-mirror and octicon-tools

* replace two wiki buttons with octicons

* remove whitespace in svg sources

* Fix filepath basename on Windows for SVG bindata (#12241)

* move octicons to devDependencies

* move back to dependencies

* move svgo to devDependencies again

Co-authored-by: Cirno the Strongest <1447794+CirnoT@users.noreply.github.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

Introduce 'make svg' which calls a node script that compiles svg files
to `public/img/svg`. These files are vendored to not create a dependency
on Node for the backend build.

On the frontend side, configure webpack using `raw-loader` so SVGs can
be imported as string.

Also moved our existing SVGs to web_src/svg for consistency.

Fixes: https://github.com/go-gitea/gitea/issues/11618