Allow for user-provided twitter credentials when self-hosting (like insta)

[Gremious]

I'm not very familiar with the project, so please correct me if I'm wrong.

Twitter posts are fetched with a guest token, which is akin to how you can browse tweets when logged out, and because of that, you can't get nsfw-tagged tweets.

https://github.com/wukko/cobalt/blob/40555a471693af9a8cfbf4be517bcfe38e023909/src/modules/processing/services/twitter.js#L96-L98

There are however gifs out there to be downloaded which are tagged nsfw but are not, like some bot accounts: e.g. this tweet fails because cobalt sees it as "sensitive content" https://twitter.com/geocitiesgifbot/status/1766208542338355583

And also we should be able to just download sensitive content too anyway.

I would like to suggest allowing some twitter token/credentials to use instead of guest, when self hosted, much like you can provide instagram ones in a file.

I haven't had the pleasure of touching twitter api's myself, though I have heard that it's a pain, so I don't know if that's possible. Maybe with a user login or something?