Updated the files.

my-app/node_modules/@schematics/angular/web-worker/files/worker-tsconfig/tsconfig.worker.json.template

@@ -0,0 +1,15 @@
+/* To learn more about this file see: https://angular.io/config/tsconfig. */
+{
+  "extends": "<%= relativePathToWorkspaceRoot %>/tsconfig.json",
+  "compilerOptions": {
+    "outDir": "<%= relativePathToWorkspaceRoot %>/out-tsc/worker",
+    "lib": [
+      "es2018",
+      "webworker"
+    ],
+    "types": []
+  },
+  "include": [
+    "src/**/*.worker.ts"
+  ]
+}

my-app/node_modules/@schematics/angular/web-worker/files/worker/__name@dasherize__.worker.ts.template

@@ -0,0 +1,6 @@
+/// <reference lib="webworker" />
+
+addEventListener('message', ({ data }) => {
+  const response = `worker response to ${data}`;
+  postMessage(response);
+});