blast furance plugin: add bar dispenser to clickbox overlay

Also added support to color the dispenser / conveyor depending on the
bar dispenser state.

These are the current expected values:

0 = No bars being processed
1 = Ores are being processed on the conveyor belt, bar dispenser cannot
be checked
2 = Bars are cooling down
3 = Bars can be collected

runelite-api/src/main/java/net/runelite/api/Varbits.java

@@ -201,6 +201,17 @@ public enum Varbits
 	 */
 	IN_GAME_BA(3923),
 
+	/**
+	 * Blast Furnace Bar Dispenser
+	 *
+	 * These are the expected values:
+	 *	0 = No bars being processed
+	 *	1 = Ores are being processed on the conveyor belt, bar dispenser cannot be checked
+	 *	2 = Bars are cooling down
+	 *	3 = Bars can be collected
+	 */
+	BAR_DISPENSER(936),
+
 	/**
 	 * Motherlode mine sack
 	 */