Add a new Danger task for CI/CD Templates Development

What does this MR do?

Currently, when developers or community contributors create a merge request that contains CI/CD template change, they tend to miss the development guide and proper review process. This MR adds a new Danger task to make the following points more explicit for the MR review phase:

• MR authors should follow CI/CD template Development Guide when they change CI/CD Templates.
• MR authors should ask CI/CD template maintainer (or trainee maintainer) to review the change.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team