private void Back_Click(object sender, RoutedEventArgs e)
        {
            PhrasalWord word = new PhrasalWord(Word.Text, Definition.Text, Example.Text);

            phrasalVerbs.WordList.Add(word);
            phrasalVerbs.SaveJson("phr.json");
            Frame rootFrame = Window.Current.Content as Frame;

            rootFrame.Navigate(typeof(vocabulary_intro), null);
        }
        private void Next_Click(object sender, RoutedEventArgs e)
        {
            PhrasalWord word = new PhrasalWord(Word.Text, Definition.Text, Example.Text);

            if (Word.Text == "" || Definition.Text == "")
            {
                return;
            }
            phrasalVerbs.WordList.Add(word);
            Word.Text       = "";
            Example.Text    = "";
            Definition.Text = "";
        }