Add badge tiers to CI/CD pages

Adds tier badges to several CI/CD pages.

doc/ci/README.md

@@ -7,7 +7,7 @@ description: "Learn how to use GitLab CI/CD, the GitLab built-in Continuous Inte
 type: index
 ---
 
-# GitLab CI/CD
+# GitLab CI/CD **(FREE)**
 
 GitLab CI/CD is a tool built into GitLab for software development
 through the [continuous methodologies](introduction/index.md#introduction-to-cicd-methodologies):

doc/ci/introduction/index.md

@@ -6,7 +6,7 @@ description: "An overview of Continuous Integration, Continuous Delivery, and Co
 type: concepts
 ---
 
-# Introduction to CI/CD with GitLab
+# Introduction to CI/CD with GitLab **(FREE)**
 
 This document presents an overview of the concepts of Continuous Integration,
 Continuous Delivery, and Continuous Deployment, as well as an introduction to

doc/ci/quick_start/index.md

@@ -5,7 +5,7 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 type: reference
 ---
 
-# Get started with GitLab CI/CD
+# Get started with GitLab CI/CD **(FREE)**
 
 Use this document to get started with
 GitLab [continuous integration](https://about.gitlab.com/stages-devops-lifecycle/continuous-integration/).