fix broken icon link in examples template

Author: tcbegley

docs/templates/macros/example-navbar.html

@@ -1,12 +1,13 @@
 {% macro example_navbar() -%}
 <nav class="navbar sticky-top navbar-expand navbar-dark bg-dark">
-    <img
-      src="/static/images/icon128x128.png"
-      width="36"
-      height="36"
-      alt="dbc logo thumbnail"
-      class="mr-2"
-    />
+    <span class="mr-2 bg-white" style="padding:2px;border-radius:4px">
+      <img
+        src="/static/images/dbciconblack128.png"
+        width="36"
+        height="36"
+        alt="dbc logo thumbnail"
+      />
+    </span>
     <ul class="navbar-nav mr-auto">
       <li class="nav-item">
         <a class="nav-link" href="/examples">Back to examples</a>