Prevent redefining 'alchemy-menubar' custom element when using Turbo

This commit uses `data-turbo-eval="false"` to prevent defefining
'alchemy-menubar' custom element when navigating between pages with
Turbo.
Without this, we are getting the following error after each
`Turbo.visit`:
```
Uncaught DOMException: CustomElementRegistry.define: 'alchemy-menubar' has already been defined as a custom element
```

app/views/alchemy/_menubar.html.erb

@@ -111,7 +111,7 @@
       </div>
     </template>
 
-    <script type="module">
+    <script type="module" data-turbo-eval="false">
       class Menubar extends HTMLElement {
         constructor() {
           super()