Add the full changelog link to the release drafter template (#2838)

Author: seisman

.github/release-drafter.yml

@@ -53,6 +53,8 @@ template: |
 
   $CHANGES
 
+  **Full Changelog**: https://github.com/$OWNER/$REPOSITORY/compare/$PREVIOUS_TAG...v$RESOLVED_VERSION
+
   ### Contributors
 
   $CONTRIBUTORS