chore: add lint-staged + husky

scripts/on-lint-error.js

@@ -0,0 +1,11 @@
+console.log(`
+
+Oops! Medusa noticed some lint or style warnings in the code for this
+commit. Your changes have been committed, but you should fix the warnings before
+creating a pull request.
+Use 'npm run lint' to manually re-run these checks. You can also disable these
+checks:
+- for a single commit: git commit --no-verify
+- for all future commits: npm run hooks:uninstall
+
+`)