Generate TypeScript npm package for the protocol definitions

[follesoe]

To make it easier to consume and work with the protocol from TypeScript we could produce TypeScript types from the Protocol Definition, and publish these as a npm package, similar to how we publish a NuGet package for dotnet. The package could be hosted on the GitHub package index.

One candidate for generating the TypeScript code is: https://github.com/stephenh/ts-proto

The npm package should be produced by a GitHub action.