docs: add better instructions for module vendoring

[willfindlay]

Folks who are new to Golang might have trouble doing the go mod tidy/vendor/verify dance. It would be nice to provide some better instructions in developer docs to avoid headaches.

[ADITYADAS1999]

hey can i work with this issue ? I just start learning Golang.🤠

[mtardy]

Hey I'm sweeping all good first issue and saw that, sorry you never got a response. I think this could be closed @willfindlay as make vendor exists now that does this and is called by make generate and make codegen. Please reopen if you think we can still improve this.