Do not throw error when width or height is zero

[hypnoce]

In case the innerWidth or height of an element is zero, the lib throws an error :

textFit/textFit.js

Line 104 in 7a1eed6

throw new Error('Set a static height and width on the target element ' + el.outerHTML +

I think we can add an option to gracefully fail and ignore those edge cases.
WDYT ?