Refactor CI/CD landing page

Restructures existing page and adds improvements.

doc/ci/docker/README.md

@@ -4,6 +4,8 @@ comments: false
 
 # Docker integration
 
-- [Using Docker Images](using_docker_images.md)
-- [Using Docker Build](using_docker_build.md)
-- [Using kaniko](using_kaniko.md)
+The following documentation is available for using GitLab CI/CD with Docker:
+
+- [Using Docker images](using_docker_images.md).
+- [Building Docker images with GitLab CI/CD](using_docker_build.md).
+- [Building images with kaniko and GitLab CI/CD](using_kaniko.md).

doc/ci/yaml/README.md

-# Configuration of your jobs with .gitlab-ci.yml
+# Configuration of your pipelines with .gitlab-ci.yml
 
 This document describes the usage of `.gitlab-ci.yml`, the file that is used by
-GitLab Runner to manage your project's jobs.
+GitLab Runner to manage your project's pipelines.
 
 From version 7.12, GitLab CI uses a [YAML](https://en.wikipedia.org/wiki/YAML)
 file (`.gitlab-ci.yml`) for the project configuration. It is placed in the root

doc/user/project/pipelines/schedules.md

-# Pipeline Schedules
+# Pipeline schedules
 
 > **Notes**:
 > - This feature was introduced in 9.1 as [Trigger Schedule][ce-10533].