Allow using Twitter lists via ID

[jtojnar]

Looks like Twitter no longer publicly uses the list slugs on the website (e.g. https://twitter.com/KevinRothrock/lists/anglophone-russia gets redirected to https://twitter.com/i/lists/43845512), which makes it confusing to subscribe to a Twitter list using selfoss.

We might want to allow entering a list id or, even better, support pasting arbitrary Twitter URL and have the spout make sense of it like the Reddit spout does.