* 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* remove outdated comment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>
