fix(app/angular): set ForkTsCheckerWebpackPlugin async to true

TypeScript errors can cause a build crash during the reload process.
The build stops at 95% and only a restart of Storybook fixes it.

app/angular/src/server/create-fork-ts-checker-plugin.ts

@@ -8,7 +8,7 @@ export default function (tsLoaderOptions: Partial<Options>) {
   if (tsLoaderOptions && tsLoaderOptions.configFile) {
     return new ForkTsCheckerWebpackPlugin({
       tsconfig: tsLoaderOptions.configFile,
-      async: false,
+      async: true,
     });
   }