Add /build/info.json

[kentcdodds]

Often it's useful to know what version of the app you're looking at is. On my apps, I generate a .json file during the build that has information about the build that's running and stick that in the public directory. For example: https://kentcdodds.com/build/info.json

This is all generated via https://github.com/kentcdodds/kentcdodds.com/blob/main/other/generate-build-info.js

I think we could adapt this for the Epic Stack. It'd be great if we could find a way for this to happen without needing to know the github repo (or only know it via environment variables so it doesn't need to be hard coded).

For some apps, you may prefer to not include the commit message, but everything else is very useful.

I'm definitely open to anyone making this contribution.