Add additional tileset and change settings to make example game

presentable.

settings.py

-GRAVITY = False
+GRAVITY = True
 SCROLLING = True
 FONT = "Roboto"

tilesets/BasicTileset_Tiles.tsx

+<?xml version="1.0" encoding="UTF-8"?>
+<tileset version="1.8" tiledversion="1.8.2" name="BasicTileset_Tiles" tilewidth="16" tileheight="16" tilecount="225" columns="15">
+ <image source="BasicTileset_Tiles.png" width="240" height="240"/>
+</tileset>