docs: Update generated CLI docs

docs/content/cli.md

@@ -599,6 +599,9 @@ the OPA configuration) against each input file. This can be overridden by
 specifying the --decision argument and pointing at a specific policy decision,
 e.g., opa exec --decision /foo/bar/baz ...
 
+Alternative Usage:
+  generate exec [<path> [...]] --stdin-input [flags]
+
 ```
 opa exec <path> [<path> [...]] [flags]
 ```