Return Tweet tombstones

[JustAnotherArchivist]

Tombstones (for the unaware, that's the grey banners like 'This Tweet was deleted by the Tweet author.' or 'You’re unable to view this Tweet because this account owner limits who can view their Tweets.' that you might see in place of an actual tweet) are currently discarded entirely. Yielding a snscrape.modules.twitter.TweetTombstone item for them would likely be a better option. It should always be possible to infer the tweet ID from the context.