Add Keys#HANGING for lanterns (SpongePowered#2438)

* Add Keys#HANGING for lanterns

* Keys.HANGING -> Keys.IS_HANGING

Author: Lignium

src/main/java/org/spongepowered/api/data/Keys.java

@@ -1385,6 +1385,11 @@ public final class Keys {
      */
     public static final Key<Value<Boolean>> IS_GRAVITY_AFFECTED = Keys.key(ResourceKey.sponge("is_gravity_affected"), Boolean.class);
 
+    /**
+     * Whether a lantern block is hanging.
+     */
+    public static final Key<Value<Boolean>> IS_HANGING = Keys.key(ResourceKey.sponge("is_hanging"), Boolean.class);
+
     /**
      * Whether a {@link Cat} is hissing.
      */