Adding documentation about GFHeader

src/rom_header_gf.c

@@ -6,6 +6,15 @@
 #include "item.h"
 #include "pokeball.h"
 
+// The purpose of this struct is for outside applications to be
+// able to access parts of the ROM or its save file, like a public API.
+// In vanilla, it was used by Colosseum and XD to access pokemon graphics.
+// 
+// If this struct is rearranged in any way, it defeats the purpose of 
+// having it at all. Applications like PKHex or streaming HUDs may find
+// these values useful, so there's some potential benefit to keeping it.
+// If there's a compilation problem below, just comment out the assignment
+// instead of changing this struct.
 struct GFRomHeader
 {
     u32 version;