Add support for WebM file format in descriptions

[blax-k]

Please confirm the following.

• I checked the existing issues for duplicate feature requests
• I have checked that this feature request is not on our roadmap

What parts of Modrinth is your feature request related too?

Website

Is your suggested feature related to a problem? Please describe.

Animated demonstrations in project descriptions currently rely on GIFs or external embeds. GIFs are very large, low quality, and lack video controls. External embeds (e.g., YouTube) dont play automatically and need an interaction, can break or add tracking. This makes it harder to show short, high-quality, looping UI demos directly in the description.

Describe the solution you'd like

Enable support for WebM or MP4 videos in project descriptions.

Describe alternatives you've considered

Animated GIFs: universally supported but extremely inefficient (10–20x larger than WebM), no real controls, poor quality, no proper alpha.
YouTube/streaming embeds: Need interaction to start playing

Additional context

Currently, WebM videos are refused to be shown.