Restrict css-minimizer-webpack-plugin version below 6 in the generator

css-minimizer-webpack-plugin v6.0.0 requires Node 18+
https://github.com/webpack-contrib/css-minimizer-webpack-plugin/releases/tag/v6.0.0

lib/generators/react_on_rails/base_generator.rb

@@ -91,7 +91,8 @@ def add_yarn_dependencies
             babel-plugin-macros"
 
         puts "Adding CSS handlers"
-        run "yarn add css-loader css-minimizer-webpack-plugin mini-css-extract-plugin style-loader"
+        # css-minimizer-webpack-plugin v6.0.0 requires Node 18+
+        run "yarn add css-loader 'css-minimizer-webpack-plugin@<6.0.0' mini-css-extract-plugin style-loader"
 
         puts "Adding dev dependencies"
         run "yarn add -D @pmmmwh/react-refresh-webpack-plugin react-refresh"