feat: [Android] adjust imports for android x. closes #173

Author: reime005

android/src/main/java/com/vydia/NotificationActionsReceiver.java

@@ -2,7 +2,7 @@
 
 import android.content.BroadcastReceiver;
 import android.content.Context;
-import android.support.annotation.Nullable;
+import androidx.annotation.Nullable;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.util.Log;

android/src/main/java/com/vydia/UploadReceiver.java

@@ -1,7 +1,7 @@
 package com.vydia.RNUploader;
 
 import android.content.Context;
-import android.support.annotation.Nullable;
+import androidx.annotation.Nullable;
 import android.util.Log;
 
 import com.facebook.react.bridge.Arguments;

android/src/main/java/com/vydia/UploaderModule.java

@@ -2,7 +2,7 @@
 
 import android.content.Context;
 import android.os.Build;
-import android.support.annotation.Nullable;
+import androidx.annotation.Nullable;
 import android.util.Log;
 import android.webkit.MimeTypeMap;