Add Underjord

Author: fhunleth

content/sponsors.html

@@ -18,6 +18,10 @@ <h3 class="title is-4 has-text-grey-dark">Platinum Sponsor</h3>
 </section>
 <section class="section has-text-centered">
   <h3 class="title is-4 has-text-grey-dark">Bronze Sponsors</h3>
+  <a href="https://underjord.io/">
+    <img src="/img/Underjord_logo.png" alt="Underjord" style="height: 100px;">
+  </a>
+  <p><p>
   <a href="https://protolux.io/">
     <img src="/img/Protolux_logo.svg" alt="Protolux Electronics" style="height: 100px;">
   </a>