Add link to privacy policy in website footer

Added link to updated privacy policy in footer of `layout.erb` for the OSS website.

website/source/layouts/layout.erb

@@ -102,6 +102,7 @@
               <li><a href="/guides/index.html">Guides</a></li>
               <li><a href="/docs/index.html">Docs</a></li>
               <li><a href="/community.html">Community</a></li>
+              <li><a href="https://www.hashicorp.com/privacy">Privacy</a></li>
               <li><a href="/security.html">Security</a></li>
               <li><a href="/assets/files/press-kit.zip">Press Kit</a></li>
             </ul>