gh-1269: Added references for argument clinic directives

[Lincoln-developer]

This pull request introduces references for argument clinic directives.

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📚 Documentation preview 📚: https://cpython-devguide--1465.org.readthedocs.build/

[Lincoln-developer]

I think we should add this directly to the Argument Clinic docs; adding them as a separate page is going to be confusing.

Okay, thanks for the review. Let me work on the requested changes.

[python-cla-bot[bot]]

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