Add FlagPlayer (YouTube Frontend WebApp)

[Seneral]

REPO: https://github.com/Seneral/FlagPlayer
Website: https://flagplayer.seneral.dev
Demo: https://flagplayer.seneral.dev/index.html?list=PL-u4nPmCTE6HrP_tMuzr_xcqimUxbkEkd&v=izsjRpcgfmk

FlagPlayer is an alternative youtube frontend focused on music playback (though it does support video playback).
The use case is to browse and find new music on youtube to add to your playlists, and when you simply want to listen, you open FlagPlayer, which consumes less resources and supports background playback (e.g. on mobile).
It doesn't have a typical homepage, instead it will show all the playlists that you have saved - of course you don't need to create your own, you can search for videos/playlists.
You can cache audio of videos manually (click on the 3dots menu of the video) and when network drops out, it will be able to play these back if they are in the playlist.
It is a web-app that works without the youtube API, and it's very lightweight. It obviously mimics the youtube design just for the sake of it. Javascript is obviously required, and it won't hide your IP from youtube, in return you don't rely on a server besides for CORS. Worst case, if no official backend is available, you can fall back to any other public CORS host, and you'd only loose comments (which do require some flags to be set which public cors servers can't).
You can host the backend yourself, in fact, I use it in a combo that starts up the local server alongside the installed web-app on my desktop PC.
I developed it 4 years ago and kept it up to date though I don't think a lot of other people ever used it much.