Added missing macos return to sysconfig.get_platform()

Author: ivanbelenky

Doc/library/sysconfig.rst

@@ -394,6 +394,7 @@ Other functions
 
    macOS can return:
 
+   - macosx-11.0-arm64
    - macosx-10.6-ppc
    - macosx-10.4-ppc64
    - macosx-10.3-i386

Lib/sysconfig/__init__.py

@@ -648,6 +648,14 @@ def get_platform():
        win-arm64 (64-bit Windows on ARM64 (aka AArch64)
        win32 (all others - specifically, sys.platform is returned)
 
+    macOS can return:
+       macosx-11.0-arm64
+       macosx-10.6-ppc
+       macosx-10.4-ppc64
+       macosx-10.3-i386
+       macosx-10.4-fat
+
+
     For other non-POSIX platforms, currently just returns 'sys.platform'.
 
     """