Let me ignore a repository so one known-bad repo stops failing every sync

[KofTwentyTwo]

One of the repositories in my org can't be cloned on Windows (it has paths Windows rejects), and another is an old one I don't care about. Every Sync and Sync All now ends red because of those two, which makes it hard to notice a real failure.

I'd like to mark a repository as ignored for an account: Sync and Sync All skip it, it shows an Ignored state in the list, it doesn't count toward Failed, and I can un-ignore it later. It should be remembered with the account so I only decide once.

Tracked as #119.