Allow for screen % inside Instance.DebugScreenText

[girlglock]

Instead of using px to specify the x and y of DebugScreenText it would be nice to have a way to use screen % to ensure the text is always in the same spot relative to the users game resolution.

example:

// prints to the middle of the screen (50%, 50%)
Instance.DebugScreenText({ text: "hello :3",
                           percent_x: 50,
                           percent_y: 50,
                           duration: 1,
                           color: { r: 255, g: 255, b: 255 }
});

// prints to lower left of the screen (90%, 5%)
Instance.DebugScreenText({ text: "hello :3",
                           percent_x: 90,
                           percent_y: 5,
                           duration: 1,
                           color: { r: 255, g: 255, b: 255 }
});