Fix Bundle size test after webpack 5 update (#10502)

PR #10186 upgraded to webpack 5, which caused the output of the bundle-size-test to be all 23 bytes with all export removed.

See #10186 (comment)

Adding `output.library` in the webpack config fixes the issue.

Author: curtisman

Diff for: examples/utils/bundle-size-tests/webpack.config.js

@@ -40,7 +40,8 @@ module.exports = {
     extensions: ['.tsx', '.ts', '.js'],
   },
   output: {
-    path: path.resolve(__dirname, 'dist')
+    path: path.resolve(__dirname, 'dist'),
+    library: 'bundle',
   },
   node: false,
   plugins: [