feat: enable audio & video for Linux targets

[TheSunCat]

Thank you so much for your contribution to FluffyChat ❤️❤️❤️

• I have read and understood the contributing guidelines.

Pull Request has been tested on:

• Android
• iOS
• Browser (Chromium based)
• Browser (Firefox based)
• Browser (WebKit based)
• Desktop Linux
• Desktop Windows
• Desktop macOS

Description

I use FluffyChat on my Linux phone (via Flatpak), and I wanted to listen to & send voice messages. This MR makes this possible by enabling the just_audio_media_kit package and initializing it.
Additionally, I enable the video player by adding the fvp dependency (not used by default on Android and iOS, though their docs encourage doing so for performance).

Before merging

How do other platforms handle audio libs? Currently I am forcing Linux to load via JustAudioMediaKit.ensureInitialized, but (probably) this should be based on the target platform. I don't have access to any others to test on though, so I figured I'd submit this MR for review and figure it out here :)

[TheSunCat]

I added another commit which fixes the video player on Linux (and probably Windows, but I don't have a machine to test on). Fixes #1516

[TheSunCat]

Fixed all the checks. Should be ready for merge, though I don't know how to edit the title of the MR to remove "WIP" 😅

[TheSunCat]

Aha, code_tests was failing 😄
just_audio_media_kit is licensed under the Unlicense which, according to this matrix (IANAL) is compatible with AGPL. Therefore I added it to licenses.yaml as permitted.

I fixed all the warnings, though I disagree with pubspec.yaml dependencies needing to be alphabetical (I would much rather put related deps together).

[krille-chan]

@TheSunCat thank you so much :-) before we merge we should check if this actually works inside of a snap and inside of a flatpak. There we might need to adjust something with the sandbox stuff

[TheSunCat]

You're welcome :)

I am rewriting the FluffyChat flatpak to build from source (developing here, not ready yet), and as part of that I noticed that the fvp package adds a new requirement on libmpv.

So this definitely has to be addressed in the snap as well before merging this.