add sound-transit.png logo for grid (#30)

Author: safrazier17

docs/img/sound-transit.png

@@ -44,6 +44,9 @@
   <div class="logo-grid__item">
     <img src="img/sumc.png" alt="Shared Use Mobility Center (SUMC)" />
   </div>
+  <div class="logo-grid__item">
+    <img src="img/sound-transit.png" alt="Sound Transit" />
+  </div>
   <div class="logo-grid__item">
     <div class="show-light-mode">
       <img src="img/taskar-light.png" alt="Taskar Center for Accessible Technology" />