[web-animations-1] Add link for EventHandler

Author: birtles

web-animations-1/Overview.bs

@@ -146,6 +146,8 @@ urlPrefix: https://html.spec.whatwg.org/multipage/webappapis.html; type: dfn; sp
     text: queue a microtask
     text: relevant Realm; url: concept-relevant-realm
     text: update the rendering
+urlPrefix: https://html.spec.whatwg.org/multipage/webappapis.html; type: interface; spec: html
+    text: EventHandler
 urlPrefix: https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html.html; type: dfn; spec: html
     text: animation frame callbacks; url: animation-frames
     text: run the animation frame callbacks