update default newsletter_sub_form.html

layouts/partials/newsletter_sub_form.html

@@ -1,8 +1,14 @@
 {{/* Add `layouts/partials/newsletter_sub_form.html` in your own code to customize the form */}}
 
 <div class="subscribe-form">
-  <form action="">
-    <input type="text" name="email" placeholder="Your email address">
-    <button>Subscribe | 订阅</button>
+  <form
+    action=""
+  >
+    <div class="input-group">
+      <input type="text" name="email" placeholder="Your email address">
+
+      <button type="submit">Subscribe<span class="hide-for-sm"> | 订阅</span></button>
+    </div>
+
   </form>
 </div>