Add vendor-prefixed user-select to code block line numbers

assets/css/bobastyle.css

@@ -833,6 +833,15 @@ code {
   display: block;
 } /* fixes line numbers on firefox when there's only one line */
 
+.chroma .lnt,
+.chroma .ln {
+  /* chroma sets the non-prefixed one only */
+  user-select: none;
+  -webkit-user-select: none;
+  -moz-user-select: none;
+  -ms-user-select: none;
+}
+
 /* }}} */
 
 /* Asides {{{ */