✨ Better twitter sharing (use configuration)

Author: borisschapira

_includes/footer.html

@@ -3,7 +3,7 @@
     <p class="col-8 sm-width-full left py-2 mb-0">This project is maintained by <a class="text-accent" href="https://github.com/{{ site.github_username }}">{{ site.github_username }}</a></p>
     <ul class="list-reset right clearfix sm-width-full py-2 mb-2 mb-lg-0">
       <li class="inline-block mr-1">
-        <a href="https://twitter.com/share" class="twitter-share-button" data-hashtags="{{ site.title }}">Tweet</a> <script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0],p=/^http:/.test(d.location)?'http':'https';if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src=p+'://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js,fjs);}}(document, 'script', 'twitter-wjs');</script>
+        <a href="https://twitter.com/share" class="twitter-share-button" {% if site.twitter_username %} data-via="{{ site.twitter_username }}" {% endif %} {% if site.twitter_hashtags %} data-hashtags="{{ site.twitter_hashtags }}" {% endif %}>Tweet</a> <script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0],p=/^http:/.test(d.location)?'http':'https';if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src=p+'://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js,fjs);}}(document, 'script', 'twitter-wjs');</script>
       </li>
       <li class="inline-block">
         <a class="github-button" href="https://github.com/{{ site.github_username }}/{{ site.github_repo }}" data-icon="octicon-star" data-count-href="{{ site.github_username }}/{{ github_repo }}/stargazers" data-count-api="/repos/{{ site.github_username }}/{{ github_repo }}#stargazers_count" data-count-aria-label="# stargazers on GitHub" aria-label="Star {{ site.github_username }}/{{ github_repo }} on GitHub">Star</a>