This will only work with black backgrounds, sorry kids. (however, if you're clever you can work around that, but I leave that to you)

First make an active object with your text, place it right below the frame. The text should be white.

Now make a gradient in graphics software of your choice. Make it go from white to black. If you want to make the text fade out as well then make the gradient black to white to black. The gradient should be the same size as your game.

Now place the gradient in the game, and set its ink effect to OR. Now for a very simple code snippet:

+Always
-Set Y position of Text to Y("Text")-1

(if the text moves too slowly, feel free trying other values)

If it won't work, make sure the gradient is layered above the text. Otherwise the gradient's OR effect will not be applied to the text.