Add copy button to markdown code blocks (#17638)

* 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* remove outdated comment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>

1 files changed, 7 insertions, 0 deletions

diff --git a/web_src/js/svg.test.js b/web_src/js/svg.test.js
new file mode 100644
index 0000000000..f1939c3a46
--- /dev/null
+++ b/web_src/js/svg.test.js
@@ -0,0 +1,7 @@
+import {svg} from './svg.js';
+
+test('svg', () => {
+  expect(svg('octicon-repo')).toStartWith('<svg');
+  expect(svg('octicon-repo', 16)).toInclude('width="16"');
+  expect(svg('octicon-repo', 32)).toInclude('width="32"');
+});