* 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>

* 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

* Consolidate Logos and update README header

- Remove unused `logo-lg.png`, `logo-sm.png` and `logo-192.png`.
- Consolidate `favicon.svg` and `logo.svg` to just `logo.svg`.
- Remove Safari Mask icon, it seems to work fine with just `favicon.png` (no SVG support).
- Remove Fluid Icon. It only served Firefox and SVG works just fine there.
- Update customization instructions.
- Update README.md to use SVG icon, increase logo size and center it and badges.

* Update README_ZH.md

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

* Update README_ZH.md

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* gitea png to logo.svg

* gitea safari svg to logo

* minify svgs

* Update english docs

* Update missing section on customizing logo

* Clean up SVG

* update per feedback

* fix css style

* Delete gitea.png

* no new line at end of file

* fix newline?

Co-authored-by: 6543 <6543@obermui.de>

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

* Rework 'make generate-images'

- Remove external dependencies and replace it with a node script that
  does does the same.
- Move detail removal from gitea-sm.png to favicon.png
- Remove favicon.ico and its generation, it is unused and we already serve
  favicon.png in its place.

Fixes: https://github.com/go-gitea/gitea/issues/12314

* use proper centering value for preserveAspectRatio

* fix lint

* use fabric

* better linting fix

* fix typo

* mention detail-remove class in docs