feat: support multiple accounts

[setchy]

This PR adds support for multiple GitHub Cloud or GitHub Enterprise Service accounts. 🎉

Majority of the code changes were to:

• pass notification object instead of its parts
• use account.token instead of deriving it from hostname (now that hostname isn't unique)
• use unique getAccountUUID for notification interactions (mark as read, raise native notifications, etc) so that state is correctly managed per account and not per hostname

Closes #365

[setchy]

I think this is ready for review and ideally further local testing.

[setchy]

looking into the test coverage drop 👀

[afonsojramos]

Locally tested and everything looks awesome! One edge case that we can improve is:

When using the same account twice (same PAT even), the dropdown doesn't work, although it does show.

[setchy]

the dropdown doesn't work, although it does show.

when you scroll, do you see the duplicate account header and notifications?
UPDATE: tested myself - it behaves as I expected (ie: showing duplicate the account details)

were you expecting it to be interactive (spoiler: i was too, but atm, it isn't)

[setchy]

One edge case that we can improve

ha - you found the edge case straight away... yep, haven't implemented any duplicate checking - figured that can just be handled by end-users :)