Enable replication over web socket

[redgeoff]

Use socket-pouch (or pieces of it) to allow multiple PouchDB instances to sync over a single web socket with a howler server

[kripper]

Check: https://github.com/pouchdb/pouchdb/issues/6528#issuecomment-1088647837

BTW, we first tried Howler but had a hard time to integrate it in our project, basically the same problem described here: https://github.com/redgeoff/couchdb-howler/issues/128#issue-956114213

We expected to find something like a JS pouchdb plugin we could easily include in our project, but then we got attracted by the idea to use socket.io.

Maybe the main difference is that Howler is not keeping long polling connections for each database which is probably better, but I guess that multiple pulls could be less or more expensive depending on the pull frequency (ie. the latency to sync updates).