New snout: Mandibles (#2589)

## About The Pull Request
Adds a new snout, sprite-work courtesy of Iska
https://github.com/NovaSector/NovaSector/pull/1754

## Why It's Good For The Game
Insert a video of a spider here

## Proof Of Testing
Trust me! (Have I ever failed you before?)

## Changelog

🆑
add: Added new snout "Mandibles (Top)"
/🆑

Co-authored-by: Jinshee <manastra2536@gmail.com>
Co-authored-by: Waterpig <49160555+Majkl-J@users.noreply.github.com>
Co-authored-by: Arturlang <24881678+Arturlang@users.noreply.github.com>

modular_zubbers/code/modules/customization/sprite_accessories/snouts.dm

@@ -25,3 +25,8 @@
 	icon = 'modular_zubbers/icons/customization/snouts.dmi'
 	icon_state = "fullalt"
 	color_src = USE_ONE_COLOR
+
+/datum/sprite_accessory/snouts/mammal/top/mandibles
+	name = "Mandibles (Top)"
+	icon = 'modular_zubbers/icons/customization/snouts.dmi'
+	icon_state = "mandibles1"