Firefox's new WebRender engine seems to have a bug with fieldsets styled
with inset box-shadows
(https://bugzilla.mozilla.org/show_bug.cgi?id=1496538).
As a workaround, use a tiny .SVG as a sliced border-image to draw the border.
Fixes #42.
* Add section in docs
* Hide range input on all browsers
Displays indicator as radio outline on Windows 10 Firefox 75
* Add svg icons
* Add thumb styling on range input
* Add track to range input
* Add indicator css for has-recatangular-indicator
* Update styling and labels for range input
* Update example for simple range input
* Remove repeated code
* Remove unused icon and add vertical input style
* Refactor styling and adapt description to fit
* Add style for all vertical lengths and update docs
* Correct 2x to 2px
