[DRAFT] Use `Shellcheck` to ensure 'correctness' of shell scripts

To Do - Complete / check the following ## What needs to change? - We should run Shellcheck on any changes to shell scripts in the repository. ## Why does it to change? - We now use the `vendorsetup.sh` script to download ***at build time*** the correct version of the components that are managed in this repository. Shellcheck helps to ensure that changes to that script (or any other scripts we may create in future) is of good enough quality. ## How does it need to change? - Shellcheck should run automatically any time a change to a shell script is pushed to github See #77 for background more info