Added theme specific logos

docs/stylesheets/custom.css

@@ -1,3 +1,13 @@
+@media screen {
+  [data-md-color-scheme=default] .logo-dark {
+    display: none !important;
+  }
+
+  [data-md-color-scheme=slate] .logo-light {
+    display: none !important;
+  }
+}
+
 a.md-header__button.md-logo > img {
   height: 50px;
 }