Add Dubious Disc Salesman

This adds the Dubious Disc Salesman to Cinnabar Pokemon Centre. I chose this area because it's late in the game and it seemed a bit iffy to constantly have to go with Pokemon Centres not in towns. Cinnabar has some connection to Silph, so it makes more sense than just balancing.

There are probably improvements that could be made (eg. a quote as you buy) but the salesman code is surprisingly brittle so I'd rather not break stuff for hours for something that already works perfectly fine.

scripts/CinnabarPokecenter.asm

@@ -7,6 +7,7 @@ CinnabarPokecenter_TextPointers:
 	dw CinnabarPokecenterText2
 	dw CinnabarPokecenterText3
 	dw CinnabarTradeNurseText
+	dw PoryZSalesmanText
 
 CinnabarHealNurseText:
 	script_pokecenter_nurse
@@ -21,3 +22,72 @@ CinnabarPokecenterText3:
 
 CinnabarTradeNurseText:
 	script_cable_club_receptionist
+
+PoryZSalesmanText:
+	text_asm
+	CheckEvent EVENT_BOUGHT_DUBIOUS_DISC, 1
+	jp c, .alreadyBoughtPoryZ
+	ld hl, .Text1
+	call PrintText
+	ld a, MONEY_BOX
+	ld [wTextBoxID], a
+	call DisplayTextBoxID
+	call YesNoChoice
+	ld a, [wCurrentMenuItem]
+	and a
+	jp nz, .choseNo
+	ldh [hMoney], a
+	ldh [hMoney + 2], a
+	ld a, $21
+	ldh [hMoney + 1], a
+	call HasEnoughMoney
+	jr nc, .enoughMoney
+	ld hl, .NoMoneyText
+	jr .printText
+.enoughMoney
+	lb bc, DUBIOUS_DISC, 1
+	call GiveItem
+	jr nc, .done
+	xor a
+	ld [wPriceTemp], a
+	ld [wPriceTemp + 2], a
+	ld a, $21
+	ld [wPriceTemp + 1], a
+	ld hl, wPriceTemp + 2
+	ld de, wPlayerMoney + 2
+	ld c, $3
+	predef SubBCDPredef
+	ld a, MONEY_BOX
+	ld [wTextBoxID], a
+	call DisplayTextBoxID
+	SetEvent EVENT_BOUGHT_DUBIOUS_DISC
+	jr .done
+.choseNo
+	ld hl, .RefuseText
+	jr .printText
+.alreadyBoughtPoryZ
+	ld hl, .Text2
+.printText
+	call PrintText
+.done
+	jp TextScriptEnd
+
+.Text1
+	text_far _PoryZSalesmanText1
+	text_end
+
+.RefuseText
+	text_far _PoryZSalesmanNoText
+	text_end
+
+.NoMoneyText
+	text_far _PoryZSalesmanNoMoneyText
+	text_end
+
+.Text2
+	text_far _PoryZSalesmanText2
+	text_end
+
+PoryZBagFull:
+	text_far _PoryZBagFull
+	text_end