Implement damage-based slowdown on TD Gunboats

In line with original.

mods/cnc/rules/ships.yaml

@@ -34,6 +34,18 @@ BOAT:
 	RejectsOrders:
 	SelectionDecorations:
 		VisualBounds: 42,24
+	GrantConditionOnDamageState@HEAVY:
+		Condition: heavy-damage
+		ValidDamageStates: Heavy
+	GrantConditionOnDamageState@CRITICAL:
+		Condition: critical-damage
+		ValidDamageStates: Critical
+	SpeedMultiplier@HEAVYDAMAGE:
+		RequiresCondition: heavy-damage
+		Modifier: 75
+	SpeedMultiplier@CRITICALDAMAGE:
+		RequiresCondition: critical-damage
+		Modifier: 50
 
 LST:
 	Inherits: ^Ship