Yes, there is an official way, but it works only while you set up the new iPhone.

1. On the iPhone start the setup from the beginning. If it is already set up, you need to erase it first. This is the catch.
2. Choose Move Data from Android during setup and install Apple's Move to iOS app on the Android phone.
3. Open Move to iOS, enter the code shown on the iPhone, and select WhatsApp in the list of data to move.
4. Then install WhatsApp on the iPhone, sign in with the same number, and tap Start when WhatsApp offers to import the chats.

Both phones must be on the same Wi-Fi, and the WhatsApp versions must be up to date. Keep the Android phone until you check the chats on the iPhone. Chats can not be moved back to Android the same way.