I'm using tsc 4.8.4 and there is no support for navigator.userActivation. This is now part of the HTML Living Standard and implemented by Chrome, Edge, and Opera browsers.
Spec: https://html.spec.whatwg.org/multipage/interaction.html#the-useractivation-interface
MDN: https://developer.mozilla.org/en-US/docs/Web/API/UserActivation
This is useful when writing JavaScript that interacts with Web API's that are gated behind user interaction, such as the Web Speech API.