Feature request: allow jpg as a synonym for jpeg in toDataURLWithMultiplier

[ghost]

I was calling canvas.toDataURLWithMultiplier('jpg',4.0), which actually returns a png image. It took me quite a while to figure out what was going on, because some of the tools I use will open a png-named-as-jpg without complaint. Others, however, understandably claim that the file is corrupted.

This was my own fault, but maybe it would save others some time if "jpg" and "jpeg" were made synonymous for this purpose.

Thanks for the great package!

[Kienz]

+1