Found [a better color picker](https://github.com/web-padawan/vanilla-colorful) that [does not rely](https://github.com/mdbassit/Coloris/issues/139) on `querySelectorAll` or a global shared instance, and is also around a third of the size of the previous one. The popover is handled by tippy.js for which I introduced a new "bare" theme and it uses a new sibling-based mechanism which should prove useful later to create tippy popovers via HTML only. <img width="846" alt="Screenshot 2024-03-31 at 04 03 38" src="https://github.com/go-gitea/gitea/assets/115237/7639b911-a2d7-4f5c-bffd-a9d84561e747">
