Update 1.21-notes.md

Author: TheRealWormbo

doc/1.21-notes.md

@@ -93,6 +93,7 @@
   * [ ] Similar to `WandHUD` there should probably be a corresponding capability for the Manaseer Monocle HUD rendering.
   * [x] `WandBindable` should be a capability and be used to bind Force Relay targets.
   * [x] `Wandable` should not be restricted to block entities and should be used for forming the Mana Enchanter and non-binding interactions with Force Relays.
+  * [ ] `Bound` should probably be a block capability
 * [ ] Check if `ManaNetworkHandler` is really still needed
   * [x] Try implementing closest collector/pool search the way the Copper Golem finds chests. (it's the only reason we maintain a collection of mana pools)
   * [ ] Figure out a different way to construct the burst trajectory visualization on the client. (that's the other reason we maintain a collection of mana collectors, even though mana collectors aren't inherently tied to firing bursts in the first place)