added toString methods

lib/hooks/hooks-frame.js

@@ -266,6 +266,7 @@ this.hooksFrame = this.hooksFrame || (() => {
 				}
 				return new FontFace(...arguments);
 			};
+			window.FontFace.toString = function () { return "function FontFace() { [native code]"; };
 		}
 
 		if (window.IntersectionObserver) {
@@ -305,6 +306,7 @@ this.hooksFrame = this.hooksFrame || (() => {
 				observers.set(intersectionObserver, { callback, options });
 				return intersectionObserver;
 			};
+			window.IntersectionObserver.toString = function () { return "function IntersectionObserver() { [native code]"; };
 		}
 	}