Add polish translation (#2926)

mods/carts/locale/carts.pl.tr

@@ -0,0 +1,6 @@
+# textdomain: carts
+Cart=Wagonik
+(Sneak+Click to pick up)=(Skradanie+Naciśnij aby zebrać)
+Rail=Tory
+Powered Rail=Napędzane tory
+Brake Rail=Hamujące tory