* 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* remove outdated comment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>

* clean up async/await, and sort init calls in `index.js
* use `const _promise` to indicate that we do not need await an async function

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

* creates and implements generic markup less class

* How to give custom CSS to externally rendered html

* Clarifies sources of CSS styling of markup

* further clarification of sources of markup styling

* rename _markdown to _markup

* remove defunct import

* fix orphaned reference

* Update docs/content/doc/advanced/external-renderers.en-us.md

* more renames markdown -> markup

* do not suggest less customization

* add back tokens

* fix class whitespace, remove useless if-clause

* remove unused csv-data rules

* use named exports and rename functions

* sort imports

Co-authored-by: HarvsG <11440490+HarvsG@users.noreply.github.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: silverwind <me@silverwind.io>

- Add loading spinners on editor and mermaid renderers
- Add error handling and inline error box for mermaid
- Fix Mermaid rendering by using the .init api

* Add mermaid JS renderer

For feature parity with GitLab. Tested in files, issues, wiki, editor.
arc-green only does an inversion because the renderer seems to like to
render white backgrounds on boxes.

Ref: https://github.com/go-gitea/gitea/issues/3340
Fixes: https://github.com/go-gitea/gitea/issues/12307

* add feature entry, switch to neutral theme, remove border

* add bindFunctions support

* remove unnecessary border-radius

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