Automated release pipeline

[tjhorner]

When publishing a new version of this extension, these manual steps need to be taken by a human (me!):

Chrome Web Store

• Log into dashboard
• Zip extension dist directory
• Upload new version
• Update metadata if needed, for e.g. new permissions or changelog
• Submit for review

Firefox Addons

• Log into dashboard
• Zip extension dist directory
• Zip extension source code (manually excluding all the stuff in the .gitignore)
• Upload new version & source code
• Write changelog and reviewer notes
• Submit for review

That's a lot of work! And, more importantly, it's work that can be done by robots. There should be a GitHub Actions workflow that performs these actions on a release:

• Automatically writes a changelog based on commit messages between last version
• Automatically packages and uploads to Chrome Web Store
• Automatically packages and uploads both distribution and source to Firefox Addons
• Uploads a .crx and .xpi as release artifacts for people that want it for some reason