docs: add notes on the vue inspect command (#3797) [skip ci]

Co-authored-by: Natalia Tepluhina <[email protected]>
Co-authored-by: Haoqun Jiang <[email protected]>

Author: 3 people

docs/guide/webpack.md

@@ -160,6 +160,11 @@ You can redirect the output into a file for easier inspection:
 ``` bash
 vue inspect > output.js
 ```
+By default, `inspect` command will show the output for development config. To see the production configuration, you need to run
+
+``` bash
+vue inspect --mode production > output.prod.js
+```
 
 Note the output is not a valid webpack config file, it's a serialized format only meant for inspection.