feat(navbar): language switcher (#760)

* feat(navbar): language switcher

* docs: add language-switch

* chore: just for the demo

* fix: drop conflicting CSS

* fix: use constant

* fix: pre-existing bug with rtl on mobile

* docs: add comment to explain the algo

* chore: more readable algo

* review

Co-authored-by: Xin <5097752+imfing@users.noreply.github.com>

* feat: different icons

* feat: icon as param

* fix: inconsitency with rtl

* fix: render inside the sidebar

* chore: remove the demo

---------

Co-authored-by: Xin <5097752+imfing@users.noreply.github.com>

exampleSite/content/docs/guide/configuration.md

@@ -69,6 +69,15 @@ There are different types of menu items:
     - name: Theme Toggle
       params:
         type: theme-toggle
+        label: true # optional, default is false
+   ```
+6. Language Switcher
+   ```yaml
+    - name: Language Switcher
+      params:
+        type: language-switch
+        label: true # optional, default is false
+        icon: "globe-alt" # optional, default is "translate"
    ```
 
 These menu items can be sorted by setting the `weight` parameter.