Add options to import and export user data

src/invidious/views/subscription_manager.ecr

@@ -2,7 +2,16 @@
 <title>Subscription manager - Invidious</title>
 <% end %>
 
-<h1><%= subscriptions.size %> subscriptions</h1>
+<div class="pure-g h-box">
+    <div class="pure-u-2-3">
+        <h3><%= subscriptions.size %> subscriptions</h3>
+    </div>
+    <div class="pure-u-1-3" style="text-align:right;">
+        <h3>
+            <a href="/data_control">Import/Export</a>
+        </h3>
+    </div>
+</div>
 
 <% subscriptions.each do |channel| %>
 <h3 class="h-box">