To fix error on Firefox 85.0.1 (Ubuntu 20.04)

On firefox, I got:
```
Uncaught TypeError: supabase.auth.user().then is not a function
    fetchUserDetails http://192.168.1.230:8080/index.js:62
    EventHandlerNonNull* http://192.168.1.230:8080/index.js:18
    EventListener.handleEvent* http://192.168.1.230:8080/index.js:10
index.js:62:6
    fetchUserDetails http://192.168.1.230:8080/index.js:62
    fetchUserDetails self-hosted:1176
    (Async: EventHandlerNonNull)
    <anonymous> http://192.168.1.230:8080/index.js:18
    (Async: EventListener.handleEvent)
    <anonymous> http://192.168.1.230:8080/index.js:10
```
My solution might not be the best but it makes it work :)

Please continue showing examples about direct access from javascript client (like Firebase do).

examples/javascript-auth/index.js

@@ -56,16 +56,10 @@ const logInSubmitted = (event) => {
 }
 
 const fetchUserDetails = () => {
-  supabase.auth
-    .user()
-    .then((response) => {
-      alert(JSON.stringify(response))
-    })
-    .catch((err) => {
-      alert(err.response.text)
-    })
+      alert(JSON.stringify(supabase.auth.user()))
 }
 
+
 const logoutSubmitted = (event) => {
   event.preventDefault()