add link to Mastodon

_config.yml

@@ -10,9 +10,10 @@ github:
 owner_url: working-group
 owner_name: the R Contribution Working Group
 image: assets/img/Rlogo-white.png
+mastodon: https://hachyderm.io/@R_Contributors
+mastodon_alt: R Contributors Mastodon profile
 twitter: R_Contributors
-twitter_alt: RCWG Twitter profile
-twitter_image: assets/img/Rlogo-white-square.png
+twitter_alt: R Contributors Twitter profile
 github: r-devel
 github_alt: R-devel GitHub organization
 navigation:

_layouts/custom.html

@@ -72,6 +72,8 @@ <h1>{{ site.title | default: site.github.repository_name }}</h1>
         {% else %}
         <p>This site is maintained by <a href="{{ site.owner_url }}">{{ site.owner_name }}</a>
         <br>
+        <a rel="me" href="{{ site.mastodon }}" target="_blank">
+	       <img src="{{ '/assets/img/mastodonlogo.svg' }}" height="20" alt="{{ site.mastodon_alt }}" style="vertical-align:middle;" border="0"></a>
          <a href="https://twitter.com/{{ site.twitter }}" target="_blank">
 	       <img src="{{ '/assets/img/twitterlogo.png' }}" height="20" alt="{{ site.twitter_alt }}" style="vertical-align:middle;" border="0"></a>
 	       <a href="https://github.com/{{ site.github }}" target="_blank">