Fixed Navbar Login/Account button on Mobile.

[Lezzz]

While trying to set-up the template for the first time I noticed that my Login button was not working on mobile and it was simply redirecting me to the main page (or to be more exact - to the /account page but I was not logged in).

The purpose of this PR is to fix the issue by adding an user check that switches between /account and /login depending on Auth state, like on Desktop.

Old behaviour:

• User can't login on mobile (unless explicitly going to /login) because the Account button is not directing to the login page first.

New behaviour:

• For logged in users, the Account button will direct them to their account page.
• For logged out users, the Account button will direct them to the login page.

Please review the changes and let me know if any further modifications are required.

+      {user ? (
       <Disclosure.Button
         as='a'
         href='/account'
         className='block px-4 py-2 text-base font-medium text-gray-500 hover:bg-gray-100 hover:text-gray-800'
       >
         Account
       </Disclosure.Button>
+      )   :   (
+        <Disclosure.Button
+        as='a'
+        href='/login'
+        className='block px-4 py-2 text-base font-medium text-gray-500 hover:bg-gray-100 hover:text-gray-800'
+      >
+        Account
+      </Disclosure.Button>
+      )}