fix: prevent unnecessary user object updates causing infinite loops

[yogeshchoudhary147]

Problem

When calling getAccessTokenSilently(), the reducer creates a new user object reference even when the user data hasn't changed. This causes infinite loops in useEffect hooks that depend on the user object.

Example scenario:

const { user, getAccessTokenSilently } = useAuth0();

useEffect(() => {
  const token = await getAccessTokenSilently();
  myFunction(token, user);
}, [user, getAccessTokenSilently]); // Infinite loop!

Solution

Use deep equality comparison (isEqual from lodash-es) instead of reference equality (===) when checking if the user object has changed in the reducer.

Changes

• Added lodash-es dependency for deep equality checking
• Updated GET_ACCESS_TOKEN_COMPLETE and HANDLE_REDIRECT_COMPLETE cases in reducer to use isEqual
• State is only updated when user content actually changes
• Tree-shakeable import adds ~1.2 KB gzipped to bundle size

Testing

• Existing tests pass
• No breaking changes
• Fixes infinite loop scenario

Fixes #787