feat: check if you're part of a group by providing the group/channel id

[msramalho]

This is particularly useful for private channels whose links are like t.me/c/12345678 where 12345678 is an id that does not map to a group name.

The goal is to accept these links as valid in the textarea (currently they are not) and visually distinguish them from the others (join vs check if joined) while still checking if an account is part of them, the tool already knows the ids of the groups the account is in, so it's just about checking the ids and displaying that.