formatting script and gh action

[interim17]

Problem

Advances #251

Solution

This addresses the first portion of work:

• defining prettier config and write and check scripts
• defines a github action to check PRs for prettier warnings/errors (doesn't make any changes or block merging)

The write script has not be run in this PR, as it will affect 200+ files, once this is approved we can run it no a branch and merge the changes, or alternately define a gh action, or use husky, to run the script automatically either before committing or when PRs are opened.

Is anyone opinionated on how the config should be set up?

• New feature (non-breaking change which adds functionality)