Add missing ext/operator documentation

Hello PHPDoc Team, I apologize for the belated introduction. I have taken over as the lead maintainer for ext/operator and I am trying to create the missing documentation for it. I was not able to find any guides for creating entirely new sections of the documentation, so I took my best guess. I have two pull requests open, one on doc-base and the other on doc-en. https://github.com/php/doc-base/pull/246 https://github.com/php/doc-en/pull/4669 Their automated workflows since they are mutually dependent on each other. As the 1 year anniversary of the opening of the PRs is approaching, I thought that I would try harder to reach out to the PHPDoc Team to see what the next steps are. Best regards, Joshua Lopez