Add linting to repo

[rcantin-w]

The current linting setup doesn't really seem to work. It'd be great to review it and make it impossible to commit code that doesn't match our standards (no unused imports, similar tabbing style, etc.)

[rcantin-w]

As discussed with @kenoir this week; we might want to look into a solution that ensure we have the same linting rules on all TS projects (so wc.org and content-api at least).