Adding documentation for git to rewrite URLs to use SSH instead of HTTPS

What does this merge request do and why?

GDK clones via HTTPS to allow for unauthenticated use. For folks who push to the repositories, they may be using SSH, which would fail in the default configuration. Updating documentation to add a workaround for this while a flag is investigated in #1670.

How to set up and validate locally

1. Run bash support/install from within a repository with this branch checked out
2. Run git config --global url.'git@gitlab.com:'.insteadOf 'https://gitlab.com/'
3. Verify GDK works as expected and that git ops are now using SSH vs HTTPS

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
  • I'm not 100% sure if this is or isn't backwards compatible
• Tests added for new functionality. If not, please raise an issue to follow-up.
  • I updated any existing tests
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.