[Bug] "NewPipe" OPML is incompatible with NewPipe

[julianfairfax]

Describe the bug
In the import/export settings of Invidious, an option to export your subscriptions as an OPML file for use with NewPipe is present. This file is not compatible with NewPipe's import/export feature.

Steps to Reproduce

1. Go to the import/export settings
2. Export an OPML file for use with NewPipe
3. Try importing it into NewPipe

Logs
NewPipe says "unable to import subscriptions" and "no file/content source)

Screenshots

Additional context
A conversion tool has been made: https://github.com/wheresalice/invidious2newpipe

[TheFrenchGhosty]

A 20$ bounty has been added to this issue.

Anyone opening a PR fixing this issue, will receive 20$ (in BTC) from the Invidious project.

More details: #1898

[SamantazFox]

@julianfairfax yes, thank you :)