Make the locale picker functional

This is limited to supported locales which currently only is 'en-US'.

Refs: #2044

assets/locale-picker.ts

@@ -1,5 +1,20 @@
 export class LocalePicker extends HTMLElement {
   static element = 'locale-picker' as const
+
+  constructor() {
+    super()
+
+    this.addEventListener('click', event => {
+      if (!(event.target instanceof HTMLElement)) {
+        return
+      }
+      const locale = event.target.dataset['locale']
+      if (locale !== undefined) {
+        document.cookie = `locale=${locale}`
+        location.reload()
+      }
+    })
+  }
 }
 
 window.customElements.define(LocalePicker.element, LocalePicker)

src/page.ts

@@ -318,7 +318,8 @@ export function page({
 
                           <locale-picker>
                             <ul>
-                              <li><a href="#">English</a></li>
+                              <li><a href="#" data-locale="en-US">English</a></li>
+                              <li><a href="#" data-locale="es-419">Spanish</a></li>
                             </ul>
                           </locale-picker>
                         </div>