fix(template-typescript-webpack): webpack entrypoint extensions (#3014)

Author: erickzhao

packages/template/typescript-webpack/tmpl/forge.config.ts

@@ -29,10 +29,10 @@ module.exports = {
           entryPoints: [
             {
               html: './src/index.html',
-              js: './src/renderer.js',
+              js: './src/renderer.ts',
               name: 'main_window',
               preload: {
-                js: './src/preload.js',
+                js: './src/preload.ts',
               },
             },
           ],