Add the ability to "upload a signature" instead of drawing it

To clarify: This is IN ADDITION TO the drawing field. Sometimes people have their signature saved as a PNG or JPG so being able to upload it instead of drawing it on their phone/computer could be useful. A little ("Or upload your signature") below the drawing field would be great. The drawing field should disappear if a user uploads a signature, and then reappear if they remove the uploaded signature.