Add external link icon (#8)

Co-authored-by: Ben Spitz <diracdeltafunk@users.noreply.github.com>

Author: StevenClontz

_includes/external-link.html

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" height="0.8em" width="0.8em" fill="currentcolor"><!--!Font Awesome Free 6.6.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free Copyright 2024 Fonticons, Inc.--><path d="M320 0c-17.7 0-32 14.3-32 32s14.3 32 32 32l82.7 0L201.4 265.4c-12.5 12.5-12.5 32.8 0 45.3s32.8 12.5 45.3 0L448 109.3l0 82.7c0 17.7 14.3 32 32 32s32-14.3 32-32l0-160c0-17.7-14.3-32-32-32L320 0zM80 32C35.8 32 0 67.8 0 112L0 432c0 44.2 35.8 80 80 80l320 0c44.2 0 80-35.8 80-80l0-112c0-17.7-14.3-32-32-32s-32 14.3-32 32l0 112c0 8.8-7.2 16-16 16L80 448c-8.8 0-16-7.2-16-16l0-320c0-8.8 7.2-16 16-16l112 0c17.7 0 32-14.3 32-32s-14.3-32-32-32L80 32z"/></svg>

_layouts/default.html

@@ -63,9 +63,15 @@
             <a href="/projects/">Projects</a>
         {% endif %}
 
-        <a href="{{site.github_url}}">GitHub</a>
+        <a href="{{site.github_url}}">
+          GitHub
+          {% include external-link.html %}
+        </a>
 
-        <a href="{{site.zulip_url}}">Zulip</a>
+        <a href="{{site.zulip_url}}">
+          Zulip
+          {% include external-link.html %}
+        </a>
 
       </nav>