Encode and decode protobuf messages

[bajtos]

Many peer-to-peer protocols serialise request and response payload using Protocol Buffers (https://protobuf.dev), for example libp2p Identify.

Zinnia should provide a recommended best practice for creating requests and parsing responses in protobuf format.

We can recommend one of the existing JS/TS implementations like protobuf.js or protobuf-ts.

Note that Zinnia does not support ES Modules yet, see #43, so module builders would have to use a bundler like esbuild to bundle their module code + all dependencies into a single JS file for Zinnia.

Another option is to provide custom Zinnia API for encoding & decoding Protobuf messages. We can start with a low-level API to encode/decode raw messages with no .proto definitions needed and then build on top of that.

Considering our limited capacity, I think it's better to leverage an existing 3rd-party implementation and focus our effort on optimising DX of using those libraries in Zinnia.

[juliangruber]

+1 for recommending protobuf.js + bundler for now, and not making it a platform feature