Patch v0.20.115

Connect achievement to Steam service
Use cache when downloading ghost in race of the day mode
Disable navigation menu when "Waiting for server" UI is displayed
Fix UI navigation with keyboard / gamepad
Fix initialization when connecting to the backend
Fix leaderboard issue in race of the day mode
Fix challenge duration to 10 minutes
Fix the possibility to create a challenge with a locked region / difficulty
Fix racer explosion when crashing on the terrain
Challenge code are now alphanumeric lower case instead of integer
Add mission button at the end of the race when a new mission is unlocked to access quickly the next mission