Allow developing with @web/dev-server (#7782)

web-dev-server.config.js

@@ -0,0 +1,24 @@
+const cors = require("@koa/cors");
+const { rollupAdapter } = require("@web/dev-server-rollup");
+
+const rollup = require("./build-scripts/rollup");
+
+const rollupWDSPlugins = rollup
+  .createAppConfig({
+    latestBuild: true,
+    isWDS: true,
+  })
+  .inputOptions.plugins.map((rollupPluginConf) =>
+    rollupAdapter(rollupPluginConf, {}, {})
+  );
+
+/** @type import("@web/dev-server/src/config/DevServerConfig.ts") */
+module.exports = {
+  mimeTypes: {
+    "**/*.ts": "js",
+    "**/*.json": "js",
+    "**/*.css": "js",
+  },
+  middleware: [cors()],
+  plugins: rollupWDSPlugins,
+};