Add JS build process

rollup.config.js

@@ -0,0 +1,21 @@
+const { resolve } = require('path');
+const babel = require('rollup-plugin-babel');
+const uglify = require('rollup-plugin-uglify');
+
+const production = process.env.NODE_ENV === 'production';
+
+module.exports = {
+  input: resolve(__dirname, 'js/index.js'),
+  output: {
+    file: resolve(__dirname, 'theme/bundle.js'),
+    format: 'iife',
+    name: 'windycoys',
+    sourcemap: !production && 'inline',
+  },
+  plugins: [
+    babel({
+      exclude: 'node_modules/**',
+    }),
+    production && uglify(),
+  ].filter(Boolean),
+};