Backport #22892
As you can imagine, for the Blender development process it is rather
nice to be able to include videos in issues, pull requests, etc.
This PR allows the `<video>` HTML tag to be used in MarkDown, with the
`src`, `autoplay`, and `controls` attributes.
## Help Needed
To have this fully functional, personally I feel the following things
are still missing, and would appreciate some help from the Gitea team.
### Styling
Some CSS is needed, but I couldn't figure out which of the LESS files
would work. I tried `web_src/less/markup/content.less` and
`web_src/less/_base.less`, but after running `make` the changes weren't
seen in the frontend.
This I would consider a minimal set of CSS rules to be applied:
```css
video {
max-width: 100%;
max-height: 100vh;
}
```
### Default Attributes
It would be fantastic if Gitea could add some default attributes to the
`<video>` tag. Basically `controls` should always be there, as there is
no point in disallowing scrolling through videos, looping them, etc.
### Integration with the attachments system
Another thing that could be added, but probably should be done in a
separate PR, is the integration with the attachments system. Dragging in
a video should attach it, then generate the appropriate MarkDown/HTML.
Co-authored-by: Sybren <122987084+drsybren@users.noreply.github.com>