Original Readme converted to markdown format

By the way, copy and paste the original PR (for the sake of security): pkp#29 (comment)

Author: kant

Readme.md

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+    =============================================
+    === pdf.js Viewer Plugin
+    === A pdf.js-based PDF viewer for OJS 3.0.x
+    === Author: Alec Smecher <[email protected]>
+    =============================================
+
+## About
+
+This is a PDF viewer plugin based on the pdf.js PDF reader.
+
+## License
+
+This plugin is licensed under the GNU General Public License v2. See the file LICENSE for the complete terms
+of this license.
+
+## Installation
+
+To install this plugin, place its files into a subdirectory of `plugins/viewableFiles` called pdfJsViewer.
+Run the upgrade script (please back up your database before doing this) to register the plugin with your
+installation of OJS.
+
+Once the plugin has been installed, use the Journal Manager's "Plugins" interface to enable it.
+
+## Contact/Support
+
+Please email the authors for support, bugfixes, or comments.