docs(api): add --silent option to cli.md (#1781)

Author: Joe Bottigliero

src/content/api/cli.md

@@ -109,6 +109,12 @@ Specifies a different [configuration](/configuration) file to pick up. Use this
 webpack --config example.config.js
 ```
 
+**Suppress output of webpack**
+
+```bash
+webpack --silent
+```
+
 **Print result of webpack as a JSON**
 
 ```bash