feat(events): Add isTopFrame to shouldStartLoadForRequest (#1537)

* Add isTopFrame to shouldStartLoadForRequest on iOS

onLoadingStart is not raised for inner frames, but onShouldStartLoadWithRequest still is. This keeps that behavior but adds isTopFrame to onShouldStartLoadWithRequest so that apps can perform their own filtering if desired.

* Update docs

Co-authored-by: Jamon Holmgren <jamonholmgren@gmail.com>

android/src/main/java/com/reactnativecommunity/webview/events/TopShouldStartLoadWithRequestEvent.kt

@@ -14,6 +14,8 @@ class TopShouldStartLoadWithRequestEvent(viewId: Int, private val mData: Writabl
 
   init {
     mData.putString("navigationType", "other")
+    // Android does not raise shouldOverrideUrlLoading for inner frames
+    mData.putBoolean("isTopFrame", true)
   }
 
   override fun getEventName(): String = EVENT_NAME