IDL: Add any support to IDL dictionary and use it in CustomEventInit

Source/core/events/CustomEventInit.idl

Index: Source/core/events/CustomEventInit.idl
diff --git a/Source/modules/app_banner/BeforeInstallPromptEventInit.idl b/Source/core/events/CustomEventInit.idl
similarity index 58%
copy from Source/modules/app_banner/BeforeInstallPromptEventInit.idl
copy to Source/core/events/CustomEventInit.idl
index fc66cc8d9a905f64723a05065d055c7281fae321..0c02acd922fcd22ed48dfde37f298ed17d9c958f 100644
--- a/Source/modules/app_banner/BeforeInstallPromptEventInit.idl
+++ b/Source/core/events/CustomEventInit.idl
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-dictionary BeforeInstallPromptEventInit : EventInit {
-    sequence<DOMString> platforms;
+// https://dom.spec.whatwg.org/#interface-customevent
+
+dictionary CustomEventInit : EventInit {
+    any detail = null;
 };