Suggesting new functions - texture foreground, text border, text thickness

[kuna]

Hello, First I want to say I'm using your library greatfully.Thanks for making this library. But I need more functions like texture foreground and so on, So I implemented it and it works well I think. It works like this.

What about these new functions? If you like it then I want to make pull request to your project.

[grimfang4]

Those look pretty nice! I'd love to see how you went about it.