Implement theme toggle in navbar.

- Add additional logic for navbar partial.
- Uses a menu item params.type of `theme-toggle`.
- Uses additional params.hideLabel boolean to set hideLabel for the theme-toggle.html partial.

layouts/partials/navbar.html

@@ -31,6 +31,8 @@
     {{- range .Site.Menus.main -}}
       {{- if eq .Params.type "search" -}}
         {{- partial "search.html" (dict "params" .Params) -}}
+      {{- else if eq .Params.type "theme-toggle" -}}
+        {{- partial "theme-toggle.html" (dict "hideLabel" (.Params.hideLabel | default true)) -}}
       {{- else -}}
         {{- $link := .URL -}}
         {{- $external := strings.HasPrefix $link "http" -}}
@@ -67,4 +69,4 @@
       {{- partial "utils/icon.html" (dict "name" "hamburger-menu" "attributes" "height=24") -}}
     </button>
   </nav>
-</div>
+</div>