Use GitHub Actions for continuous deployment

[Michael-F-Bryan]

In the long term it'll probably be easier to wire up GitHub Actions so that every push to master gets automatically deployed to the dev.hotg.ai site.

I imagine we'll be able to get 90% of the way there by copying the main example from GitHub Actions for Firebase. Then we just need to set up protected branches so all changes need to go through a PR (possibly requiring reviews to merge).

[kthakore]

make sure you rune the node script (see package.json build command) to add analytics to the html.