Adding gitlab migration guide

Author: Ahmed Bilal

content/actions/migrating-to-github-actions/index.md

@@ -0,0 +1,15 @@
+---
+title: Migrating to GitHub Actions
+intro: 'Migrate from other continuous integration (CI) providers to {{ site.data.variables.product.prodname_actions }}.'
+productVersions:
+  actions: '*'
+  enterprise: '>=2.22'
+---
+
+{{ site.data.reusables.actions.enterprise-beta }}
+{{ site.data.reusables.actions.enterprise-github-hosted-runners }}
+
+{% link_in_list /migrating-from-circleci-to-github-actions %}
+{% link_in_list /migrating-from-gitlab-to-github-actions %}
+{% link_in_list /migrating-from-azure-pipelines-to-github-actions %}
+{% link_in_list /migrating-from-jenkins-to-github-actions %}