Document sAreaGlowTilemapMapping

I used a script to generate the format for the array, so I can easily
change its formatting if needed.

include/constants/maps.h

@@ -9,4 +9,10 @@
 #define MAP_GROUP(map) (MAP_##map >> 8)
 #define MAP_NUM(map) (MAP_##map & 0xFF)
 
+// These groups are used by pokedex_area_screen.c to find wild
+// pokemon locations.
+#define MAP_AREA_OVERWORLD_MONS MAP_GROUP(PETALBURG_CITY)
+#define MAP_AREA_SPECIAL_MONS_1 MAP_GROUP(METEOR_FALLS_1F_1R)
+#define MAP_AREA_SPECIAL_MONS_2 MAP_GROUP(SAFARI_ZONE_NORTHWEST)
+
 #endif  // GUARD_CONSTANTS_MAPS_H