Add ActiveSupport require for Rails 5.2-6.0 compatibility

The compact_blank method used in ensure_webpack_generated_files_exists
was introduced in Rails 6.1. By requiring active_support/core_ext/enumerable,
we ensure this method is available in Rails 5.2-6.0 environments.

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

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

Author: justin808

lib/react_on_rails/configuration.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 # rubocop:disable Metrics/ClassLength
 
 module ReactOnRails