Make select size required

Author: habohlin

Form-Controls/index.html

@@ -71,7 +71,8 @@ <h1>Product Pick</h1>
               <label for="white">Brown</label>
             </section>
             <label for="size">Choose a size:</label>
-            <select id="size">
+            <select name="size" id="size" required>
+              <option></option>
               <option value="xs">XS</option>
               <option value="s">S</option>
               <option value="m">M</option>