Provide option to filter docs

[AkshayWarrier]

From discussion #52 (comment), most people might not need most of the docs that are shipped by default, therefore it makes sense to provide an option to filter docs according to user preference. It might also make up for faster load times. We can have something similar to DevHelp

[bragefuglseth]

Something that would require less user effort is to have a favorites section in the top of the sidebar that people can put the libraries they use the most in.

Benefits:

• Instead of having to manually uncheck everything that's not used, people can explicitly mark the few things they actually use
• If, by chance, another library is actually needed, it's still easily reachable

The load times won't improve this way, but UX-wise I think it would be better.

[AkshayWarrier]

Maybe we could have both? Having a favorites section might help with easier browsing but some uncommon docs such as atspi or dex may never even be used by users, and the search results get cluttered with items the user doesn't even care about. So I do think there should still be some way to globally enable/disable certain docsets.