Updates to main.cpp, gameStage.h, maps.h
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Main.cpp
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- Moved the gameStage enumeration definition to GameStage.h

GameStage.h
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- Defined quit() function.
- Defined some code in game() function to test processMap() and renderMap()
- Changed game(), quit() and mainMenu() functions to accept a reference to a gameStage enumeration. This is to allow the functions to modify the gameState.

Maps.h
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- Updated the renderMap() function to create tiles of 3x3 instead of 1x1