feat(code): add copy button for code (#239)

assets/css/_mixin/_compatibility.scss

@@ -41,8 +41,8 @@
   display: -webkit-box;
   display: box;
 
-  -moz-box-orient: $orient;
   -webkit-box-orient: $orient;
+  -moz-box-orient: $orient;
   box-orient: $orient;
 }
 
@@ -67,3 +67,21 @@
     color: $color;
   }
 }
+
+@mixin max-content($property) {
+  #{$property}: -webkit-max-content;
+  #{$property}: -moz-max-content;
+  #{$property}: intrinsic;
+  #{$property}: max-content;
+}
+
+@mixin tab-size($value) {
+  -moz-tab-size: $value;
+  -o-tab-size: $value;
+  tab-size: $value;
+}
+
+@mixin appearance($value) {
+  -moz-appearance: $value;
+  -webkit-appearance: $value;
+}