Need embed fonts to be optional

[davidburns573]

Our team uses a number of font families that are very large when included in the <style/> tag of the exported svg. This results in image files that are 10000x larger. We would like to optionally disable the embedFonts step of the conversion process.

We've temporarily forked this repo and made our change, but it would be great if we could include this here since others may benefit as well!

Forked repo: https://github.com/davidburns573/dom-to-image-more