Declare compatibility with PEP 751

Author: zklaus

peps/pep-0780.rst

@@ -146,6 +146,15 @@ from GIL-enabled as default to free-threading as default over time.
 The ABI features are designed with this in mind to guarantee usefulness and
 simplicity for the foreseeable future in a changing Python ecosystem.
 
+Relation to Other PEPs
+----------------------
+
+This PEP extends environment markers with set semantics for ABI features.
+:pep:`751#additions-to-marker-expression-syntax` includes a similar extension
+for lock file specific environment markers; although the two have been
+developed indepedently, they are compatible where they overlap in terms of the
+new set semantics.
+
 Specification
 =============