Docs: Convert PEP 630 (Isolating Extension Modules) to a HOWTO (GH-94489)

Co-authored-by: Stanley <[email protected]>
Co-authored-by: Alex Waygood <[email protected]>

Author: 3 people

Doc/howto/index.rst

@@ -31,4 +31,5 @@ Currently, the HOWTOs are:
    clinic.rst
    instrumentation.rst
    annotations.rst
+   isolating-extensions.rst