chore: updated ci.yml to fix typo in comment (#254)

Author: ota-meshi

.github/workflows/ci.yml

@@ -109,7 +109,7 @@ jobs:
               run: |
                   npm run test
 
-                  # Load src/index.js to check for syntax errors.
+                  # Load src/index.mjs to check for syntax errors.
                   # This is because for some reason the exit code does not become 1 in Node.js 12.
                   # See https://github.com/eslint-community/eslint-utils/pull/253
                   node src/index.mjs