Create instructional video for Learn about horizontal scaling

We need a video covering the basics of git for #1593 (closed). Once the video is completed, please upload the video to the Onboarding Folder' in Google drive. If you recorded the video using Zoom, please upload the video+audio version of it so it contains everything.

If your video needs editing, please ping myself (@jcolyer) in this issue and I would be more than willing to do this for you!

The video should cover the following:

Checklist:

• Understand the basics of horizontal scaling
• Setup a highly available GitLab instance

Documentation:

• Scaling and High Availability
• Horizontal Scaling
• Fully Distributed