getEventByRevision for mongodb and tingodb

[robinfehr]

haven't updated the readme due to not having it implemented for all db's yet.

[adrai]

alternative:

es.getEventStream(query, revMin, revMax, (err, stream) => {
  stream.events[0]
})

[susannaroden]

Hey everyone 👋

New maintainer here… we, i.e. @thenativeweb, have taken over the responsibility to maintain this module from @adrai, and I would like to give a little update on this PR:

As Adriano already pointed out this can easily be done using the getEventStream function, so introducing a new function for a pretty specific special case is probably not the way to go. Besides, this PR is unfortunately incomplete and lacks any update for the documentation, hence I am going to close this one.