Fix Incorrect Context

• The OneSignalPlugin was initializing the native OneSignal SDK with an incorrect context. Switched to using the flutter registrar's activeContext instead.
• This would have caused the SDK to always believe that the app was not currently in focus, meaning the SDK would ignore the current inFocusDisplayType option and always show notifications as normal Android notifications

Author: Nightsd01

android/src/main/java/com/onesignal/flutter/OneSignalPlugin.java

@@ -98,7 +98,7 @@ else if (call.method.contentEquals("OneSignal#didSetNotificationOpenedHandler"))
 
   private void initOneSignal(MethodCall call, Result result) {
     String appId = call.argument("appId");
-    Context context = flutterRegistrar.context();
+    Context context = flutterRegistrar.activeContext();
 
     OneSignal.Builder builder = OneSignal.getCurrentOrNewInitBuilder();
     builder.unsubscribeWhenNotificationsAreDisabled(true);
@@ -164,8 +164,8 @@ private void getPermissionSubscriptionState(Result result) {
   }
 
   private void setInFocusDisplayType(MethodCall call, Result result) {
-    int deplayType = call.argument("displayType");
-    OneSignal.setInFocusDisplaying(deplayType);
+    int displayType = call.argument("displayType");
+    OneSignal.setInFocusDisplaying(displayType);
     result.success(null);
   }