Make the creative mod hand dig 'dig_immediate' nodes fast

Engine change now makes this possible.

mods/creative/init.lua

@@ -54,6 +54,9 @@ if creative_mode_cache then
 				snappy  = caps,
 				choppy  = caps,
 				oddly_breakable_by_hand = caps,
+				-- dig_immediate group doesn't use value 1. Value 3 is instant dig
+				dig_immediate =
+					{times = {[2] = digtime, [3] = 0}, uses = 0, maxlevel = 256},
 			},
 			damage_groups = {fleshy = 10},
 		}