Change languages settings' behaviour

[ghost]

• I carefully read the contribution guidelines and agree to them.
• I checked if the issue/feature exists in the latest version.

Hi,
I just finished the translation of Esperanto (I didn't translate everything alone, thank you other translators) on Weblate and noticed that there is a problem with it.

Currently, the languages settings' behaviour is the following:
− "Default content country" especially changes Trendings page (I didn't see what else).
− I have no clue what default content language changes.
− There is no way to change the app's language from the app, you must change your phone's app.

The last point is the problem, as Esperanto is a constructed international auxiliary language, almost everyone who speak it also speak another language (the ~2000 native speakers are bilingual (or even more), and the other speakers — about ten millions in the world — also speak their native language);
and isn't translated on every software, including phones' OS.
Therefore you won't be able to change NewPipe into Esperanto even though the community made an effort to translate to Esperanto.

What I think we should have in NewPipe: 
− By default, NewPipe's language is your phone's language (as it's now).
− "Default content language" changes NewPipe's language.
Or a third language option but that would confuse people, then you should clarify what they actually do in the settings, so that people aren't lost.

Also, reCAPTCHA string should not be let translatable (as NewPipe, MD5 or SHA-1 is), because it's causing "Failed check: Unchanged translation"