Account for very large text deltas (due to Copy & Paste etc.)

[adzialocha]

With gossip we have a max. message limit which is an issue, as these diffs can become very large. I believe that's due to a wrong use of Automerge but we'll run into the same issue sooner or later even with Automerge correctly used, for example when someone copy & pastes are large text into a document at once.

The current limit is 4096 bytes (temporarily increased to a higher number), that's roughly a text of 4096 characters, without any CRDT meta info or p2panda operation header.

This we can solve by chopping the text up into multiple, smaller "edits" and send one p2panda operation per edit