Convert top gulp modules to ESM (#16387)

build-scripts/gulp/demo.js

@@ -0,0 +1,45 @@
+import gulp from "gulp";
+import env from "../env.cjs";
+import "./clean.cjs";
+import "./entry-html.cjs";
+import "./gather-static.cjs";
+import "./gen-icons-json.cjs";
+import "./rollup.cjs";
+import "./service-worker.cjs";
+import "./translations.cjs";
+import "./webpack.cjs";
+
+gulp.task(
+  "develop-demo",
+  gulp.series(
+    async function setEnv() {
+      process.env.NODE_ENV = "development";
+    },
+    "clean-demo",
+    "translations-enable-merge-backend",
+    gulp.parallel(
+      "gen-icons-json",
+      "gen-pages-demo-dev",
+      "build-translations",
+      "build-locale-data"
+    ),
+    "copy-static-demo",
+    env.useRollup() ? "rollup-dev-server-demo" : "webpack-dev-server-demo"
+  )
+);
+
+gulp.task(
+  "build-demo",
+  gulp.series(
+    async function setEnv() {
+      process.env.NODE_ENV = "production";
+    },
+    "clean-demo",
+    // Cast needs to be backwards compatible and older HA has no translations
+    "translations-enable-merge-backend",
+    gulp.parallel("gen-icons-json", "build-translations", "build-locale-data"),
+    "copy-static-demo",
+    env.useRollup() ? "rollup-prod-demo" : "webpack-prod-demo",
+    "gen-pages-demo-prod"
+  )
+);