Create a "GitLab Pages Onboarding" page

To improve the onboarding experience to Gitlab, I'm suggesting to create a yaml-file builder that will be visible when Pages is not deployed yet.

Idea

Inspired by other SSG-Hosting sites, developers can expect a simple, three-step process to configure their Static Site Deployment online. The configuration with a yaml-file complicates this somewhat, but also allows for more flexibility. By creating a visual Yaml-File builder, we're offering both the simplicity of a three-step onboarding process and a low-key introduction to working with yaml files.

Demos

• https://youtu.be/SOTda1E6iQ4
• https://youtu.be/iouVys2_kps
• https://youtu.be/3d1yAM34Dq4

Issues

• This relies on the @project.pages_deployed? attribute to decide whether this onboarding screen is shown or not. @project.pages_deployed however can be false if the yaml file is valid, but the pipeline is not complete/failed/... - Probably necessary to introduce a pages_onboarding_completed property.
• handling of Branches needs to be re-considered. The branch defined in the yaml may be a different one to the one the file is committed to, currently resulting in a unhandled state.
• Other SSG Sites usually offer to configure the name of the output folder. I've put that in as a placeholder, however, Pages does not currently accept any folder name other than public. This introduces friction, as it still requires editing the App's config files for most frameworks. I think removing this requirement from GitLab would massively improve the UX

To do

• Add Placeholder before LCP
• Flash / Highlight changed Lines in Editor
• Add test coverage