CI: added ESP-IDF component build (closes #1599)

extras/ci/espidf/main/main.cpp

@@ -0,0 +1,16 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright Benoit Blanchon 2014-2021
+// MIT License
+
+#include <ArduinoJson.h>
+
+extern "C" void app_main() {
+  char buffer[256];
+  StaticJsonDocument<200> doc;
+
+  doc["hello"] = "world";
+  serializeJson(doc, buffer);
+  deserializeJson(doc, buffer);
+  serializeMsgPack(doc, buffer);
+  deserializeMsgPack(doc, buffer);
+}