protobuf example (do not merge)

[skearnes]

@mikennel hopefully this is useful?

There are a few ideas that are baked into the current editor design:

• We can build up protos on the JS side and then serialize them and send them over to python for validation. This example shows validation of an entire reaction, but we can send submessages as well.
• We can fetch and/or manipulate reactions in python and then serialize them and send them over to JS for display.

[mikennel]

Examples were really helpful, thanks @skearnes !