build: add function type annotation for bazel win32 build support

Due to the file structure of Bazel Windows builds, type annotations are
required in certain locations to successfully build the project. Function
return type annotations are generally recommended anyway within the code.

Author: clydin

packages/angular_devkit/build_angular/src/tools/esbuild/javascript-transformer-worker.ts

@@ -25,7 +25,9 @@ interface JavaScriptTransformRequest {
 const textDecoder = new TextDecoder();
 const textEncoder = new TextEncoder();
 
-export default async function transformJavaScript(request: JavaScriptTransformRequest) {
+export default async function transformJavaScript(
+  request: JavaScriptTransformRequest,
+): Promise<unknown> {
   const { filename, data, ...options } = request;
   const textData = typeof data === 'string' ? data : textDecoder.decode(data);