Add font-stretch utility classes

[cyruscuenca]

Reference:
https://developer.mozilla.org/en-US/docs/Web/CSS/font-stretch

Expected format:
font-stretch-<condensed | normal | expanded | ultra-expanded>
or perhaps
font-stretch-<10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90| 100 | 110 | 120 | and so on... >

I checked for results on Google and didn't find much. No references in GitHub's repository search either.