add external link icon

Signed-off-by: Toshaan Bharvani <toshaan@vantosh.com>

themes/openpowerfoundation/layouts/join/single.html

@@ -70,7 +70,7 @@
                             </div>
                             <div class="h2">{{ .title }}</div>
                             <p>{{ .text }}</p>
-                            <p><a class="btn-outline-primary btn-sm btn" href="{{ .cta_url }}">{{ .cta_text }}</a></p>
+                            <p><a class="btn-outline-primary btn-sm btn" href="{{ .cta_url }}">{{ .cta_text }}&nbsp;<i class="fas fa-external-link-alt"></i></a></p>
                         </article>
                   {{ end }}
             </div>