Github action to build pdf output

[dearlordylord]

Hey,

This PR adds a GitHub action that [on master push] uses a published latex docker container to automatically compile a pdf. I found it useful since for some reason the container proposed in README fails to build on my machine.

This action would create a separate commit in master [that does not retrigger the build] i.e.

The result of running looks like this:

Take a look in case you'd find it usable for yourself or for other users 😄 I have set up this for myself and thought it'd be cool to share. Feel free to adjust it for yourself.