Update contribute docs to clarify adding/running prettier locally

### Describe the bug

A clear and concise description of what the bug is.

It seems the prettier buid is failing on PRs that are coming from certain places. I think the fix might be to make sure that everyone who contributes has Prettier locally and runs the write and check functions on the files they're editing.

I would probably update the docs to reference: https://prettier.io/docs/en/install.html