Add option for user to import/export their data.

[omarroth]

For folks who want to run their own instance, they should be able to export subscriptions, preferences, etc and upload to their own instance. Should also be able to migrate subscriptions/preferences e.g. from Google to Invidious account, and vice versa.

[xKeiro]

Not sure if possible, but it would be awesome if you could import/export and merge your data from Newpipe as well!

[omarroth]

@xKeiro I'm taking a look at NewPipe, but I'm having trouble finding info on exporting/importing subscriptions and other info. The best I can find is this, which makes it look like it exports in JSON format, but I don't have a device I could test the app on. If it's possible, could you provide an example of NewPipe's export format?

[xKeiro]

@omarroth
This is exactly how it exports (I didn't zip it it was zipped already):
NewPipeData-20180728_173624.zip
Edit: ^this is the export for every data: history, subscriptions, playlists

And here's the export format for just the subscriptions (note: I had to put this in a zip, so i could upload it to GitHub, it comes as a single JSON file)
newpipe_subscriptions_201807281741.zip

Tried including channels with foreign characters (Korean, Japanese) just in case

[omarroth]

Subscriptions-only look easy enough.
It looks like watch history is included in the first export though, so I think I'll close #40 before tackling it.

Looks like NewPipe uses the OPML file from YouTube, so Invidious can just export that.