docs: Add optional GitHub Actions workflow step to show last registration

[sualeh]

Add a step to the GitHub Actions workflow to show the results of the publish operation.

Motivation and Context

It shows the success of the publish operation with the id of the registration on the MCP Server Registry.

How Has This Been Tested?

By publish my own MCP Server with this workflow step included.

Breaking Changes

No.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] Documentation update

Checklist

• [x] I have read the MCP Documentation
• [N/A] My code follows the repository's style guidelines
• [N/A] New and existing tests pass locally
• [N/A] I have added appropriate error handling
• [x] I have added or updated documentation as needed

Additional context

None.