Added a note to tag the wiki when doing feature releases

Fixes https://github.com/libsdl-org/SDL/issues/12618

docs/release_checklist.md

@@ -15,6 +15,8 @@
 
 * Create a GitHub release and attach the archives you just generated.
 
+* If this is a feature release, also tag the sdlwiki with the same tag.
+
 ## New feature release
 
 * Update `WhatsNew.txt`