Update CI YAML parameter table w/ 'include'

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/56172

changelogs/unreleased/56172-docs-fix-add-include-to-ci-param-list.yml

+---
+title: Update CI YAML param table with include
+merge_request: !24309
+author:
+type: fixed

doc/ci/yaml/README.md

@@ -57,6 +57,7 @@ A job is defined by a list of parameters that define the job behavior.
 |---------------|----------|-------------|
 | [script](#script)                                | yes      | Defines a shell script which is executed by Runner |
 | [extends](#extends)                              | no       | Defines a configuration entry that this job is going to inherit from |
+| [include](#include)                              | no       | Defines a configuration entry that allows this job to include external YAML files |
 | [image](#image-and-services)                     | no       | Use docker image, covered in [Using Docker Images](../docker/using_docker_images.md#define-image-and-services-from-gitlab-ciyml) |
 | [services](#image-and-services)                  | no       | Use docker services, covered in [Using Docker Images](../docker/using_docker_images.md#define-image-and-services-from-gitlab-ciyml) |
 | [stage](#stage)                                  | no       | Defines a job stage (default: `test`) |