README.md: Update

Author: adriendupuis

tools/api_refs/README.md

@@ -112,9 +112,10 @@ fi;
 With [GitHub CLI `gh`](https://cli.github.com/), you can trigger a GitHub Action workflow to build the API References
 
 ```bash
-gh workflow run api_refs.yaml -f version=<tag> -f use_dev_version=<false|true> --ref <branch>
+gh workflow run api_refs.yaml -f version=<tag> -f use_dev_version=<false|true> --ref <branch> - f base_branch=<branch>
 ```
 
 `-f version=<tag>` to pass the Ibexa DXP version tag for which the API References are built.
 `-f use_dev_version=<false|true>` to use the released version designed by the tag, or to use the development version (`v5.0.x-dev`) for an incoming tag.
 `--ref <branch>` to use the `api_refs.yaml` workflow from a given branch instead of the default branch (`5.0`).
+`-f base_branch=<branch>` to use the `api_refs.sh` from a given branch and make a PR to that branch.