You can do this with Webcore, but there’s a simpler way. 
Simply use a virtual device which is both a sensor and a switch. Then turning on the switch with any method, including smartlighting, a voice assistant, toggling in the mobile app, etc will make the sensor look active and turning it off makes it look inactive.
People most commonly do this with a virtual contact sensor (so switch on =sensor open), but you can do it with a motion sensor as well.
No webcore required.
This is a very popular method for integration with Echo routines, but also works with IFTTT. Just remember to authorize the switch in the SmartThings app for use by IFTTT.
You can see how this is done including sample code for the dual purpose virtual device in the community FAQ: