Add docs

common/src/main/java/me/shedaniel/architectury/extensions/ItemExtension.java

@@ -24,6 +24,9 @@ import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
 import org.jetbrains.annotations.Nullable;
 
+/**
+ * Extensions to {@link net.minecraft.world.item.Item}, implement this on to your item.
+ */
 public interface ItemExtension {
     /**
      * Invoked every tick when this item is equipped.