adding prefixed versions of min and max content keywords

Author: rachelandrew

flexbox/ratios/min-max-content.html

@@ -62,10 +62,12 @@
 
   <style class="editable">
       .min-content {
+        width: -moz-min-content;
         width: min-content;
         border: 2px dotted rgb(96, 139, 168);
       }
       .max-content {
+        width: -moz-max-content;
         width: max-content;
         border: 2px dotted rgb(96, 139, 168);
       }
@@ -83,10 +85,12 @@
   </section>
   <textarea class="playable-css">
         .min-content {
+          width: -moz-min-content;
           width: min-content;
           border: 2px dotted rgb(96, 139, 168);
         }
         .max-content {
+          width: -moz-max-content;
           width: max-content;
           border: 2px dotted rgb(96, 139, 168);
         }