Add a full-fledged media viewer + support for more media types

[alexmodrono]

• I know that I'm requesting a feature for Codename Starlight (SwiftUI) and not for Hyperspace Desktop (JS).

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We can't see videos, nor GIFs, and we can't see Images in full-screen.

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Add a full-fledged media viewer as well as support for more media types.

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Writing a full-fledged media viewer in pure SwiftUI so that it works on macOS, iPadOS, and iOS.

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This is just so we can track this task's progress on our Kanban. It is already being worked on at data/media

[alexmodrono]

I made a kanban to track the progress.