Add more tilemap documentation

include/tileMap.h

@@ -0,0 +1,13 @@
+#ifndef TILEMAP_H
+#define TILEMAP_H
+
+#include "global.h"
+
+// gMapDataTopSpecial and gMapDataBottomSpecial are tileMaps of 8x8 pixels. But they are also reused for other data in
+// other parts of the game.
+
+// Rendered tileMaps https://www.coranac.com/tonc/text/regbg.htm#sec-map
+extern u16 gMapDataTopSpecial[0x4000];
+extern u16 gMapDataBottomSpecial[0x4000];
+
+#endif // TILEMAP_H