Adds Highlander Style: The Martial Art of Highlanders

Adds a new martial art: Highlander Style!
- Wielders of the powerful Highlander claymores are imbued with this
mythical prowress. Should your both your hands ever lack a grip on a
Highlander claymore, you will relinquish your newfound skill.
- Highlander Style grants immunity to ranged attacks and an unwavering
distain of cowardly guns. Just like with Sleeping Carp, you will deflect
projectiles and cannot fire guns (but can pick them up to throw in the
trash where they belong).

Adds new weapon: Highlander Claymore
- Grants the wielder the Highlander Style while held in either hand.
- Normal claymores were left in, but do not provide the martial art (so
they are "safe" to use outside highlander)

Minor refactor to martial arts which prevent use of guns.
- No longer relies on the name of the style, but rather the new
aptly-named var: `can_use_guns`

🆑
rscadd: Adds Highlander Style, granted to the wielder of Highlander
Claymores. This martial art allows you to deflect ranged attacks from
the weapons of COWARDS. FOR THE HONOR OF THE HIGHLANDERS!
tweak: Highlander now equips combatants with a Highlander claymore
instead of a normal claymore. FIGHT ON BROTHERS!
/🆑

code/game/objects/items/weapons/highlander_swords.dm

@@ -0,0 +1,46 @@
+
+//Highlander Style Martial Art
+//	Prevents use of guns, but makes the highlander impervious to ranged attacks. Their bravery in battle shields them from the weapons of COWARDS!
+
+/datum/martial_art/highlander
+	name = "Highlander Style"
+	deflection_chance = 100
+	can_use_guns = 0
+	no_guns_message = "You'd never stoop so low as to use the weapon of a COWARD!"
+
+
+//Highlander Claymore
+//	Grants the wielder the Highlander Style Martial Art
+
+/obj/item/weapon/claymore/highlander
+	name = "Highlander Claymore"
+	desc = "Imbues the wielder with legendary martial prowress and a nigh-unquenchable thirst for glorious battle!"
+	var/datum/martial_art/highlander/style = new
+
+/obj/item/weapon/claymore/highlander/equipped(mob/user, slot)
+	if(!ishuman(user))
+		return
+	var/mob/living/carbon/human/H = user
+	if(slot == slot_r_hand || slot == slot_l_hand)
+		if(H.martial_art && H.martial_art != style)
+			style.teach(H, 1)
+			to_chat(H, "<span class='notice'>THERE CAN ONLY BE ONE!</span>")
+	else if(H.martial_art && H.martial_art == style)
+		style.remove(H)
+		var/obj/item/weapon/claymore/highlander/sword = H.is_in_hands(/obj/item/weapon/claymore/highlander)
+		if(sword)
+			//if we have a highlander sword in the other hand, relearn the style from that sword.
+			sword.style.teach(H, 1)
+
+	return
+
+/obj/item/weapon/claymore/highlander/dropped(mob/user)
+	if(!ishuman(user))
+		return
+	var/mob/living/carbon/human/H = user
+	style.remove(H)
+	var/obj/item/weapon/claymore/highlander/sword = H.is_in_hands(/obj/item/weapon/claymore/highlander)
+	if(sword)
+		//if we have a highlander sword in the other hand, relearn the style from that sword.
+		sword.style.teach(H, 1)
+	return