added addthis social share

Author: shadowcodex

_includes/footer.ext

@@ -1,3 +1,4 @@
 <footer>
     <p>Made with <span class="text-danger">&#x2764;</span> by <a href="https://shadowcodex.github.io/">shadowcodex</a></p>
-</footer>
+</footer>
+<script type="text/javascript" src="//s7.addthis.com/js/300/addthis_widget.js#pubid=ra-59bfcf084d642670"></script>