GitLab Runner How-To - Add Colima troubleshooting guide

What does this Merge Request do and why?

For the Gitlab Runner + Docker configuration, the /tmp/gitlab-runner directory (where the /etc/gitlab-runner volume is mapped to) is not writable by Colima given base configurations.

This adds a link to a comment detailing how to resolve this issue.

Note: it seems like the commit before this one introduced trailing spaces. I'm using the WebIDE and the trailing spaces were automatically removed. Hope that's okay!

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.