Adds decal version of recharge floor (#91545)

## About The Pull Request

Extracts the recharge floor icon into a decal you can put on any floor

## Why It's Good For The Game

Sometimes mappers want to use alternate floor types in their mech bays
and it gets annoying to have to pick between "use normal iron floors" or
"use recharge floors"

## Changelog

🆑 Melbert
qol: Mappers can put recharge floors on any floor type
/🆑

code/game/objects/effects/decals/turfdecal/markings.dm

@@ -585,3 +585,5 @@
 /obj/effect/turf_decal/board_letter/h
 	icon_state = "board_h"
 
+/obj/effect/turf_decal/recharge
+	icon_state = "recharge"