CI/CD Home - Static representation of .gitlab-ci.yml

For part 1 outlined in &4540 (comment 424441378).

In this step, we should create two to three MRs to:

• create the new page (do the plumbing to get the Vue there, add the link to the menu, add the feature flag)
• instantiate the Editor Lite showing the project's main .gitlab-ci.yml but have it not be interactive
• show the visualization tab in the Editor Lite

the new home page is behind ci_pipeline_editor_page feature flag