Add support for extracting YouTube categories

[ghost]

Checklist

• [X] I am aware that this issue is being opened for the NewPipe Extractor, NOT the app, and my feature request will be dismissed otherwise.
• [X] I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• [X] I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• [X] This issue contains only one feature request.
• [X] I have read and understood the contribution guidelines.

Feature description

NewPipe currently has no way of recommending content so adding support for YouTube's categories could be a good add.

Why do you want this feature?

Adding YouTube's categories will make finding new videos easier.