Types of ad placements as defined by Google: https://developers.google.com/ad-placement/docs/placement-types
start: Your game has loaded, the UI is visible and sound is enabled, the player can interact with the game, but the game play has not started yet.
pause: The player pauses the game.
next: The player navigates to the next level.
browse: The player explores options outside of gameplay.
reward are reserved for special ad calls. Do not pass these types to any ads API calls.
ads.showRewarded() which will automatically add the 'reward' type.