Add instructions for linting and formatting back to CONTRIBUTING.md

[jaydeluca]

What needs to be changed? As a contributor, I would like documentation for how to ensure my code is formatted properly before submitting PRs.

There used to be a section titled "Submitting a change" that documented the npm run test-and-fix command, which can catch issues recommends running npm run fix:format to fix them.

This information was removed in this PR, so I want to raise this issue before going ahead and adding it back, in case it was intentional and preferred not to be there.

I would like to add these back if there is no objection.

What is the name + path of the page that needs changed? /CONTRIBUTING.md