Although we are not integrated with Microsoft Teams, you can still add a Teams link to your event through an email.
When a contact registers for your event you can have an email sent to them with the Teams link.
Go to the "Confirmation Emails" tab in your event set up and note down the details of the confirmation email which is found in the "Event Delegate Confirmation" section
Go to Creative tab -> Email and find your confirmation email. In the email design add the Teams link.
Now those going to your event will have the link in their email to join your webinar.