Use AndroidX

app/src/main/java/com/hippo/ehviewer/client/EhEngine.java

@@ -16,10 +16,10 @@
 
 package com.hippo.ehviewer.client;
 
-import android.support.annotation.Nullable;
 import android.text.TextUtils;
 import android.util.Log;
 import android.util.Pair;
+import androidx.annotation.Nullable;
 import com.hippo.ehviewer.AppConfig;
 import com.hippo.ehviewer.GetText;
 import com.hippo.ehviewer.R;