Add .npmrc to prettierignore

Prettier was trying to parse .npmrc as YAML and failing because it's
actually INI format. Add it to .prettierignore to skip formatting checks.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

.prettierignore

@@ -1,5 +1,7 @@
 node_modules/
 package.json
+# pnpm config file (INI format, not parseable by prettier)
+.npmrc
 # Exclude pro package (has its own formatting)
 react_on_rails_pro/
 packages/react-on-rails-pro-node-renderer/tests/fixtures/projects