Setup code formatter - prettier

[anuveyatsu]

Acceptance criteria

• [x] I can run yarn format to format my code
• [x] When I commit, it auto formats my code

Tasks

• [x] Install and setup prettier
• [x] Setup pre commit hooks, see example here https://gitlab.com/datopian/clients/national-grid/-/blob/staging/package.json#L51-58

[lauragift21]

@anuveyatsu I can take this and #21 on if you don't mind

[anuveyatsu]

@lauragift21 sure - just assigned it to you 👍