Support for viewBox property

[Aremu Oluwagbamila (SMOG)]

Hi Sara,

I observed that the exported jsx doesn't have viewBox property.

Without it, if you try to make the icon responsive by adjusting the sizes on mobile or tablet, it gets cut off.

What I have being doing is to manually add the viewBox property and the icon can be used at various sizes across various screens.

Thank you once again for this amazing plugin