Add version note for custom coverage badges

doc/ci/pipelines/settings.md

@@ -310,6 +310,8 @@ https://example.gitlab.com/<namespace>/<project>/badges/<branch>/coverage.svg?st
 
 ### Custom badge text
 
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/17555) in GitLab 13.1.
+
 The text for a badge can be customized. This can be useful to differentiate between multiple coverage jobs that run in the same pipeline. Customize the badge text and width by adding the `key_text=custom_text` and `key_width=custom_key_width` parameters to the URL:
 
 ```plaintext