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-pageUp.svg

@@ -0,0 +1,12 @@
+<!-- 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 
+   transform='rotate(90) translate(0, -16)'
+   d="M15 7H3.414l4.293-4.293a1 1 0 0
+0-1.414-1.414l-6 6a1 1 0 0 0 0 1.414l6 6a1 1 0 0 0 1.414-1.414L3.414 9H15a1 1 0 0
+0 0-2z">
+</path>
+</svg>