Add inline source maps to JavaScript files

Resolves #10

webpack.mix.js

@@ -15,6 +15,14 @@ const tailwindcss = require('tailwindcss')
  |
  */
 
+// Provide inline source maps.
+if ( ! mix.inProduction()) {
+  mix.webpackConfig({
+    devtool: 'inline-source-map',
+  })
+    .sourceMaps()
+}
+
 mix.js('resources/js/app.js', 'public/js')
   .postCss('resources/css/app.css', 'public/css', [
     cssImport(),