This includes a tool to update the various files in the repo that need
to change when a version increments.
It also includes a workflow to trigger the action manually, passing it a
version & a changelog url. It'll update the values, build the app, build
the doc, make a commit in a branch, and create a pull request to merge
this stuff back into dev.
Rewrote the changelog script to use primarily merged pull requests
between "commit A" and "commit B".
It uses the GitHub rest api. The resulting data is pushed to a draft gist.
Manual usage is in the README.
Also adds a GitHub workflow action to run the tool on demand, through
the GitHub action's interface.
