SSBC: Record brief demonstration video for running batch changes server-side

Created by: courier-new

Video should be inserted into the modal with information about setting up server-side batch changes: Figma.

• A video is better than a GIF and can just be made to look like a GIF, like the video at the top of the getting started page that just plays automatically and doesn't have any sound
• Video should roughly follow this script:
  • Pick a relevant example batch spec from examples repo, or from recent memory, and prepare at least 5 repositories across different code hosts that are indexed by your instance and that would be affected by the batch spec
  • Start from SSBC editor, with batch spec already pasted, but remove the last command from the steps
  • Start recording
  • Retype last command from the steps
  • Change at least one execution option
  • Preview workspaces
  • Execute spec
  • Select a workspace
  • Expand the logs as it's processing
  • Focus on the changeset diff once it finishes
  • Select another workspace and pretend to review the diff
  • Go to the preview
  • Select all changesets and change action to "Publish as Draft"
  • Click "Apply"
  • Wait for changesets to finish processing
  • Stop recording
  • If that's too long, you can cut out the parts where it's loading in post 😉
• Video should be prepared as both an mp4 and webm
  • The mp4 file for the video should be < 5MB
  • The webm file for the video should be < 1MB
• The video files should be uploaded to our GCP storage bucket, under sourcegraph-assets/batch-changes (where the getting started video also is)