Added a header to simplify library usage

test/JsonVariant_Invalid_Tests.cpp

@@ -5,12 +5,9 @@
 // https://github.com/bblanchon/ArduinoJson
 
 #include <gtest/gtest.h>
-#include <ArduinoJson/JsonArray.hpp>
-#include <ArduinoJson/JsonObject.hpp>
+#include <ArduinoJson.h>
 #include "Printers.hpp"
 
-using namespace ArduinoJson;
-
 class JsonVariant_Invalid_Tests : public ::testing::Test {
  public:
   JsonVariant_Invalid_Tests() : variant(JsonVariant::invalid()) {}