Add to function call to create condition

firestore.rules

@@ -27,6 +27,7 @@ service cloud.firestore {
       // it's 3 characters long, and not a prohibited combination.
       allow create: if isAuthedUser(request.auth) &&
                        inCharLimit(request.resource.data.playerInitials) &&
+                       isValidCharacter(request.resource.data.character) &&
                        !prohibited(request.resource.data.playerInitials);
     }
   }