Merge in dungeon map changes (#1)

known issues:
- in-room stairs in door shuffle draw slightly bugged sometimes
- entrance sprites in non-doors are sometimes drawn on the wrong floor
- in some modes, sanctuary will open HC map instead of sewers/HC2 map

Reviewed-on: #1
Co-authored-by: Kara Alexandra <ardnaxelarak@gmail.com>
Co-committed-by: Kara Alexandra <ardnaxelarak@gmail.com>

gk/gloom.asm

@@ -0,0 +1,29 @@
+AdjustDefaultGraphics:
+	JSL $80E310
+
+	LDA.l ChallengeModes : AND.b #$03 : CMP.b #$02 : BEQ .gloom
+	RTL
+
+.gloom
+	LDA.b #$80
+	STA.w $2115
+
+	REP #$20
+	LDA.w #$7500
+	STA.w $2116
+
+	LDY.b #SkullGfx_end-SkullGfx
+	LDX.b #$00
+
+-	LDA.l SkullGfx, X
+	STA.w $2118
+	INX #2
+	DEY #2
+	BNE -
+
+	SEP #$20
+	RTL
+
+SkullGfx:
+	incbin "data/skull.bin"
+.end