Replace :root with html

Author: reinink

src/css/preflight.css

@@ -26,7 +26,8 @@
 6. Use the user's configured `sans` font-variation-settings by default.
 */
 
-:root, :host {
+html,
+:host {
   line-height: 1.5; /* 1 */
   -webkit-text-size-adjust: 100%; /* 2 */
   -moz-tab-size: 4; /* 3 */