Add PDF Shortcut (#672)

* Add Blogtrottr as newsletter provider

* Fixed absLangURL issue with sections in footer

* Added embed-pdf shortcode

pdf-js is sered locally to preserve privacy and comply with GDPR

Co-authored-by: Emruz Hossain <hossainemruz@gmail.com>

static/js/pdf-js/web/images/toolbarButton-sidebarToggle.svg

@@ -0,0 +1,4 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16"><path d="M3 1h10a3.008 3.008 0 0 1 3 3v8a3.009 3.009 0 0 1-3 3H3a3.005 3.005 0 0 1-3-3V4a3.013 3.013 0 0 1 3-3zm11 11V4a1 1 0 0 0-1-1H8v10h5a1 1 0 0 0 1-1zM2 12a1 1 0 0 0 1 1h4V3H3a1 1 0 0 0-1 1v8z"></path><path d="M3.5 5h2a.5.5 0 0 0 0-1h-2a.5.5 0 0 0 0 1zm0 2h2a.5.5 0 0 0 0-1h-2a.5.5 0 0 0 0 1zm1 2h1a.5.5 0 0 0 0-1h-1a.5.5 0 0 0 0 1z"></path></svg>