Add LinkedIn logo badge from https://brand.linkedin.com/downloads

Author: jasongrout

_includes/biocard.html

@@ -19,7 +19,7 @@
         <a href="https://github.com/{{ include.gh_handle }}" rel="noopener noreferrer"><img src="/assets/badges/github.svg" alt="GitHub"></a>
       {% endif %}
       {% if include.linkedin %}
-        <a href="{{ include.linkedin }}" rel="noopener noreferrer">LinkedIn</a>
+        <a href="{{ include.linkedin }}" rel="noopener noreferrer"><img src="/assets/badges/linkedin.png" alt="LinkedIn"></a>
       {% endif %}
       {% if include.twitter_handle %}
         <a href="https://twitter.com/{{ include.twitter_handle }}" rel="noopener noreferrer"><img src="/assets/badges/twitter.svg" alt="Twitter"></a>