* 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>

* Add copy button to markdown code blocks

Done mostly in JS because I think it's better not to try getting buttons
past the markup sanitizer.

* add svg module tests

* fix sanitizer regexp

* remove outdated comment

* vertically center button in issue comments as well

* add comment to css

* fix undefined on view file line copy

* combine animation less files

* Update modules/markup/markdown/markdown.go

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

* add test for different sizes

* add cloneNode and add tests for it

* use deep clone

* remove useless optional chaining

* remove the svg node cache

* unify clipboard copy string and i18n

* remove unused var

* remove unused localization

* minor css tweaks to the button

* comment tweak

* remove useless attribute

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

* Drop data-original from clipboard

data-original attribute was removed. Instead, the original value from
data-content is set after success/fail message was displayed.

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* "Copy branch name" button in pull request

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Update templates/repo/issue/view_title.tmpl

Co-authored-by: silverwind <me@silverwind.io>

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: zeripath <art27@cantab.net>

* Re-allow clipboard copy on non-https sites
* fallback clipboard functions

* split `index.js` to separate files

* tune clipboard

* fix promise

* fix document

* remove intermediate empty file

* fix async event listener

* use `export function` instead of `export {}`, add more comments

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

Use async clipboard api [1] over this dependency, saving around 10kB
bundle size before minify while delivering the same functionality.

The issue comment button works but does not have a popup indication. We
could add some toast-style notifications in the future to fix that but I
think it's out of scope of this PR.

[1] https://developer.mozilla.org/en-US/docs/Web/API/Clipboard/writeText

* rework eslint config

- use explicit config that only enables rules
- upgrade eslint to 7.1.0
- add new plugins with selected rules enabled
- fix discovered issues, remove global wipPrefixes

* remove if

* undo template change

* add disabled rules as well for easier config updating

* add missing disabled rule

* update eslint and plugins

* fix new violation

* remove deprecated rules

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

- lowercase all js filenames except Vue components
- enable new lint rules, mostly focused on shorter code
- autofix new lint violations
- apply misc transformations indexOf -> includes and onevent-> addEventListener

Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>

- created lazy-loaded webpack chunk for clipboard.js
- upgraded clipboard.js from 1.5.9 to 2.0.4
- parallelize initialization of all lazy-loaded features

Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>