Add Shopify token regexes

What does this MR do?

Hopefully this is the right repo! We would like to contribute these patterns that match Shopify API secrets to make sure folks are aware when they accidentally commit them to GitLab (public or private).

What are the relevant issue numbers?

There is not an associated issue for this. I can create one, though!

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer