WhatsApp's Web extension now officially supports Microsoft's Edge Web browser. This was first noticed by users on Reddit. Until now, the functionality was officially only available on Chrome, Firefox, Opera, and Safari.
It was not that users of Microsoft's Web browser were completely out of luck until now - there was a way out using which they could access WhatsApp Web on the browser. But it's always good to see official support arriving for the software you use.
A quick look at the Reddit thread reveals that not every Microsoft Edge user is currently able to access WhatsApp Web. If that's the case for you, too, probably you need to wait a bit more given the possibility that the support is being currently rolled-out.