Add user argument docs to incidents command

src/groups/moderation/commands.rs

@@ -106,6 +106,14 @@ impl Command<State, Extras> for IncidentsCommand {
         vec![Box::new(BotModeratorPermission)]
     }
 
+    fn arguments(&self) -> &'static [Argument] {
+        &[Argument {
+            name: "user",
+            is_optional: false,
+            is_greedy: false,
+        }]
+    }
+
     fn show_in_help(&self, _rt: &Runtime<State, Extras>, extras: &Extras) -> bool {
         extras.user.is_moderator
     }