Get generated stuff out of PRs to make them cleaner

[glitch003]

I want to get all the generated code out of PR's, so that the PR only contains the code changes themselves.

This is a first pass at this:

• Remove any version info from the generated readme. Instead, we use NPM badges that just show the latest version.
• Remove "last modified" time from autogen_internal-dev.js - this info is in git already
• Run prettier after build, so that our checked in code and our generated JSON files all match

[MaximusHaximus]

👍 less churn on standard builds is a good thing IMO :) LGTM

[Ansonhkg]

lgtm!