Add Custom RSS Feeds as A Subscription

[jhlee2222]

Is your feature request related to a problem? Please describe.
Subscription management isn't as robust as I'd like, but I don't really need it to be, as another solution could curate that for me with this feature.

Describe the solution you'd like
Add the ability to subscribe to a custom RSS feed containing YouTube videos.

Describe alternatives you've considered
I'm not sure where to begin, but I've wondered if there was a way to "hack in" a subscription, maybe via the import functionality, to have it refer to a custom RSS feed. Just messing around, I've not found a way to do this. The front end likewise does not appear to allow for it either.

Additional context
I'd like the ability to manage subscriptions via my feed reader, subscribing to a YouTube channel's RSS feed, then using my feed reader to fashion a custom feed for my Invidious instance to pick up and display as though it's a channel's feed. My feed reader configuration could filter out things from subscriptions I don't care for, or could even provide a feed of videos I've tagged within the feed reader to mark to watch later. From Invidious's standpoint, I'd have one or more subscriptions that are coming from a custom RSS feed, not a channel feed directly from Youtube.

[unixfox]

I'm sorry this is out of scope.