The new beta version of WhatsApp ver. 2.20.271 now supports QR codes and this is still in development. This version is only available for beta testers only, so hold for the upcoming updates for the standard version of WhatsApp. In the future updates could be available on the Google Play Store anytime when the update goes on the air.
WhatsApp has recently enabled the support for QR codes in the latest iOS beta updates on TestFlight and it is also officially rolling out the feature for all Android beta testers, download on Google Play Store.
Features in both platforms were implemented in the same way: practically you can discover your personal QR Code visiting WhatsApp Settings. If you see a QR Code, the feature is already available for you!

When you visit the setting section you will see a QR code. Now you are ready to share this QR code with your friends or new friends. And this is really a great feature to add quickly to their contact list.

Note: when you share your personal QR Code, you’re also sharing your phone number.
You can also change this QR code from time to time when your QR code goes in the wrong hands or whenever you need to take action.

When you share a QR Code, other people can scan it opening the Scan Code tab:

You get this feature when you update the WhatsApp version to ver. 2.20.271. You can join the WhatsApp beta program on Google Play Store, just scroll down and you can see below the review section:

If the beta program is full you should wait for public rollout.
iOS users can join the beta program via TestFlight if the slot is available. If the slot is not open then you can wait for public release.