Make media buffer size configurable

[nakic]

Checklist

• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• I have read the FAQ and my problem isn't listed.
• I'm aware that this is a request for NewPipe itself and that requests for adding a new service need to be made at NewPipeExtractor.
• I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

A buffer is used to avoid interrupting media streaming during short network outages. Make it possible to configure the size of that buffer.

Why do you want this feature?

I find myself frequently (2-10 times a day) in situations in which playback will be interrupted because mobile data was unavailable for more than say 30s: this happens while in some elevators, garages etc. If I could configure NP to use a larger buffer (at the cost of a bit longer playback start latency, I assume), I could probably avoid a large share of these interruptions altogether.

Furthermore, because experience so far has shown that NP goes into all kinds of corner cases (some of them not supported that robustly) under these circumstances, many times I've had to kill NP, start it again, find the playlist I was listening to, find the video, find the part of the video etc., which is a bit tedious.

Additional information

I imagine a new entry under "Settings" to do this in one form or another (hard to say more without knowing more about the implemented buffering logic). A single field accepting a number (representing the actual buffer size or a percentage of the currently default buffer size) would probably do the trick.