Add jni interface and kotlin API examples for TTS. (#381)

sherpa-onnx/csrc/offline-tts-vits-model.h

@@ -8,6 +8,11 @@
 #include <memory>
 #include <string>
 
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 #include "onnxruntime_cxx_api.h"  // NOLINT
 #include "sherpa-onnx/csrc/offline-tts-model-config.h"
 
@@ -18,6 +23,9 @@ class OfflineTtsVitsModel {
   ~OfflineTtsVitsModel();
 
   explicit OfflineTtsVitsModel(const OfflineTtsModelConfig &config);
+#if __ANDROID_API__ >= 9
+  OfflineTtsVitsModel(AAssetManager *mgr, const OfflineTtsModelConfig &config);
+#endif
 
   /** Run the model.
    *