Implement code annotations in GitHub Action runner

[alerque]

@nebularg's implementation of Luacheck as a GitHub Action has a nice annotator that converts Luacheck's output to GitHub's annotation output format. It would be nice to implement something similar here too.

https://github.com/nebularg/actions-luacheck/blob/master/action.yml#L65-L85

It might be possible to just switch to the TAP output format and have GitHub process that, or if not at least the output formatter options might make it easier to implement this with less code.

[cooljeanius]

Is this the same thing as making the results available under the "Code Scanning" section of the "Security" tab, or is that something else?