Merged PR 7638: add what's new entry for user activity docs

add what's new entry for user activity docs

Author: TylerMSFT

windows-apps-src/whats-new/windows-10-build-17134.md

@@ -66,7 +66,7 @@ Private Audience | If you want your app’s Store listing to be visible only to
 Progressive Web Apps | Microsoft Edge and UWP web apps now support [Progressive Web Apps (PWAs)](https://docs.microsoft.com/microsoft-edge/progressive-web-apps)! </br> * Using [standards-based web technologies](https://developer.mozilla.org/Apps/Progressive) and [feature detection](https://docs.microsoft.com/microsoft-edge/progressive-web-apps/windows-features), you can enhance your web apps to provide native app experiences, including push notifications, offline support, and OS integration, while still offering a great baseline web app experience on browsers and platforms that don’t yet support PWA technologies. </br> * [Adding a manifest file](https://docs.microsoft.com/microsoft-edge/progressive-web-apps/get-started) to your app enables it to be installed across the entire UWP device family (including secure [Windows 10 S-mode devices](https://www.microsoft.com/windows/windows-10-s)) and distributed from the [Microsoft Store](https://docs.microsoft.com/microsoft-edge/progressive-web-apps/microsoft-store). </br> PWAs are a natural evolution of *Hosted Web Apps*, but with standards-based support for offline scenarios, thanks to the *Service Workers*, *Cache*, and *Push APIs*.
 Screen capture | The [Windows.Graphics.Capture namespace](https://docs.microsoft.com/uwp/api/windows.graphics.capture) provides APIs to acquire frames from a display or application window, to create video streams or snapshots to build collaborative and interactive experiences. See [Screen capture](../audio-video-camera/screen-capture.md) for more information.
 System Triggers | The [CustomSystemEventTrigger](https://docs.microsoft.com/uwp/api/windows.applicationmodel.background.customsystemeventtrigger) allows you to define a system trigger when the OS doesn't provide a system trigger that you need. Such as when a hardware driver and the UWP app both belong to 3rd party, and the hardware driver needs to raise a custom event that its app handles. For example, an audio card that needs to notify a user when an audio jack is plugged in.
-User Activities | The **UserActivitySessionHistoryItem** class has new methods that retrieve recent user activities. See [GetRecentUserActivitiesAsync](https://docs.microsoft.com/uwp/api/windows.applicationmodel.useractivities.useractivitychannel.getrecentuseractivitiesasync), and its overload, for details.
+User Activities | New [UserActivity documentation](../launch-resume/useractivities.md) explains how to help users resume what they were doing in your app, even across multiple devices.</br>The **UserActivitySessionHistoryItem** class has new methods that retrieve recent user activities. See [GetRecentUserActivitiesAsync](https://docs.microsoft.com/uwp/api/windows.applicationmodel.useractivities.useractivitychannel.getrecentuseractivitiesasync), and its overload, for details.
 Windows Mixed Reality APIs | To support the growing Windows Mixed Reality platform, new APIs have been added to the [Windows.Graphic.Holographic](https://docs.microsoft.com/uwp/api/Windows.Graphics.Holographic) and [Windows.UI.Input.Spatial](https://docs.microsoft.com/uwp/api/Windows.UI.Input.Spatial) namespaces.
 Windows Mixed Reality docs | The Windows Mixed Reality developer guidance is [now hosted on docs.microsoft.com.](https://docs.microsoft.com/windows/mixed-reality/) Just like in these UWP docs, you can now file feedback with GitHub Issues or submit your own contributions via a pull request.