fix(group): fix getting group members count

Closes #1303

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

js/src/graphql/group.ts

@@ -186,6 +186,9 @@ export const GROUP_BASIC_FIELDS_FRAGMENTS = gql`
         ...PostBasicFields
       }
     }
+    members {
+      total
+    }
   }
   ${ACTOR_FRAGMENT}
   ${ADDRESS_FRAGMENT}