refactor(css): remove browser prefix

* To be added back using autoprefixer

themes/typing/source/css/_source.css

@@ -1,9 +1,8 @@
 @charset "utf-8";
-
+@import "sanitize/*"; /**/
 
 button,
 input,
-optgroup,
 select,
 textarea {
   font-family: inherit;
@@ -23,8 +22,6 @@ pre {
   background: #f8f8f8;
   border: 1px solid #ddd;
   padding: 1em 1.5em;
-  display: block;
-  -webkit-overflow-scrolling: touch;
 }
 
 hr {
@@ -965,8 +962,6 @@ pre .keyword {
   width: 85%;
   padding-left: 0.2em;
   box-sizing: border-box;
-  -moz-box-sizing: border-box;
-  -webkit-box-sizing: border-box;
 }
 
 /* highlight the text box when focused */
@@ -1027,7 +1022,6 @@ svg#link {
   /* use grid to display each link in new line */
   #mobile-menu-toggle:checked + .mobile-nav-link {
     display: grid;
-    display: -ms-grid;
   }
 }
 
@@ -1085,9 +1079,6 @@ svg#link {
   line-height: 1em;
   padding: 5px;
   user-select: none;
-  -webkit-user-select: none;
-  -moz-user-select: none;
-  -ms-user-select: none;
 }
 
 .copy-button:hover {