Theme tweaks (#32)

* Bold selected navbar items for accessibility

* Include dark mode icon

Author: MGibson1

docusaurus.config.js

@@ -54,6 +54,7 @@ async function createConfig() {
           logo: {
             alt: "Bitwarden Logo",
             src: "img/logo.svg",
+            srcDark: "img/logo-white.svg",
           },
           items: [
             {

src/css/custom.css

@@ -40,3 +40,8 @@
 .navbar__logo {
   height: 2.8rem;
 }
+
+.navbar__link--active,
+.menu__link--active {
+  font-weight: bold;
+}