Updated the index.rst in the monthly meeting repository by adding the last meeting link

Author: Unique-Usman

docs/monthly-meeting/index.rst

@@ -33,3 +33,4 @@ Monthly reports in reverse chronological order.
    Sep 2023 <2023-09.md>
    Oct 2023 <2023-10.md>
    Nov 2023 <2023-11.md>
+   Dec 2023 <2023-12.md>