Adds speedloaders to the indie viper guncase. (#3676)

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## About The Pull Request

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Adds 357 speed loaders to the indie viper guncase.

## Why It's Good For The Game

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benefit the game. If you can't justify it in words, it might not be
worth adding. -->
Consistency with the syndicate viper guncase as that one got
speedloaders included. Having to buy however many 750 credits
speedloaders you needed tacked on a lot of extra cost to the indie
viper.
## Changelog

:cl:
add: Indie Viper guncase comes with 2 speedloaders.
/:cl:

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code/game/objects/items/storage/filled_guncases.dm

@@ -60,6 +60,7 @@
 
 /obj/item/storage/guncase/pistol/viper
 	gun_type = /obj/item/gun/ballistic/revolver/viper/indie
+	mag_type = /obj/item/ammo_box/a357/empty
 
 /obj/item/storage/guncase/pistol/ringneck
 	gun_type = /obj/item/gun/ballistic/automatic/pistol/ringneck/indie