Should this project contain the code for a simple yet flexible GitHub Action that allows repo maintainers to quickly add automated shellcheck testing on all pull requests submitted to their repos?

Putting that code into this repo or another koalaman repo will focus development efforts on a single, community-supported GitHub Action for shellcheck instead of a multitude of homegrown solutions.

Currently you must be in the GitHub Action beta to be able to use Actions.

https://github.com/marketplace/actions/haskell-linter