feat: Rewrote inventory handling basing on ESCItems (#417)

Co-authored-by: Dennis Ploeger <develop@dieploegers.de>

game/items/inventory/empty_sheet.esc

@@ -0,0 +1,19 @@
+:look
+say player "It's a sheet of blank paper."
+stop
+
+:pickup
+set_global i/r5_empty_sheet true
+set_active r5_empty_sheet false
+
+
+# The following action is deactivated because r5_pen ESXC script holds a similar action that is configured as one-way
+# You can try to uncomment this action here and test that action will work in both ways but with slightly different execution
+#:use r5_pen
+#say player "Ok, let's write down something on this paper."
+#set_angle player 0
+#wait 2
+#set_angle player 180
+#say player "Alright! I wrote something on it."
+#set_global i/r5_empty_sheet false
+#set_global i/r5_filled_sheet true