Add Zapier trigger that fires when Documents are updated

[rossmeissl]

@tommoor I haven't tested this yet — just wondering if you'd be interested in a PR like this before I spend more time on it.

This is just a copy of the original document trigger with a synthetic compound id that includes the document's revision as a suffix. The Zapier docs on "update triggers" are a bit bare but I believe this is how it works.

My one concern is that if a single Document is updated multiple times (i.e. multiple Revisions are created) in quick succession (i.e. within the polling interval), the Zap will trigger once for each of them. I suppose this is intended behavior on the Zapier platform.

[tommoor]

just wondering if you'd be interested in a PR like this before I spend more time on it.

Yep, not sure when I'll be able to test – but if it works then would happily accept the trigger

[rossmeissl]

Thanks @tommoor !