EC: handle back navigation from the webview

EC: remove native header

updated element call to 0.13.0-rc1

ElementX/Sources/Screens/CallScreen/CallScreenModels.swift

@@ -56,6 +56,8 @@ enum CallScreenJavaScriptMessageName: String, CaseIterable {
     case showNativeOutputDevicePicker
     /// Used to determine if the webview has selected the earpiece or not.
     case onOutputDeviceSelect
+    /// Used to handle the webview back button
+    case onBackButtonPressed
     
     private var postMessageScript: String {
         switch self {
@@ -87,6 +89,12 @@ enum CallScreenJavaScriptMessageName: String, CaseIterable {
                 window.webkit.messageHandlers.\(rawValue).postMessage(id);
             };
             """
+        case .onBackButtonPressed:
+            """
+            window.controls.\(rawValue) = () => {
+                window.webkit.messageHandlers.\(rawValue).postMessage("");
+            }
+            """
         }
     }