provide `lint` command

Summary: Provide a lint command analogous to the one in each repo, e.g. from ui-users:

Details: This should allow most lint-related dependencies to be centralized within stripes-cli and eslint-config-stripes instead of being federated across every single UI repo, drastically reducing the blast area in case of future problems like .

This needs to be thought through carefully, in particular considering whether we can continue to allow apps to depend on different versions of eslint-config-stripes so that updates to lint rules remain opt-in.