gamewindow api

[GameParrot]

Adds various game window api functions:

• game_window_get_primary_window: Returns a handle to the primary window
• game_window_is_mouse_locked: Returns if the mouse is currently locked
• game_window_get_input_mode: Returns the current input mode
• game_window_add_keyboard_callback: Adds a keyboard input callback
• game_window_add_mouse_button_callback: Adds a mouse click callback
• game_window_add_mouse_position_callback: Adds a mouse position callback
• game_window_add_mouse_scroll_callback: Adds a mouse scroll callback
• game_window_add_window_creation_callback: Adds a window creation callback

[ChristopherHX]

For consistency it could be helpful if all input methods have callbacks?

Missing gamepad.

Other than renaming this should be ready to go.