Message builder

[stefanvanburen]

One thing that's really annoying when using something like buf curl or similar CLI tools is just building a valid message. Wondering if building a message builder with something like https://github.com/charmbracelet/huh would be valuable. (I think a form-builder would be good, that could spit out protojson / pbtxt or whatever, but also interesting would be on-the-fly syntax checking/suggestions, although that might not be as easily integrated with this particular tool.)