title: how to set title and subtitle at the bottom of App Bar in flutter
body: <p>I am designing a sign in page in that, I wanted to show my title and subtitle at the bottom of App bar but not finding the proper way</p>
  <p>i used this code:</p>
  <pre><code>  @override
     Widget build(BuildContext context) {
     return Scaffold(
     appBar: PreferredSize(
     preferredSize: Size.fromHeight(150.0),
       child: AppBar(
          centerTitle: false,
          titleSpacing: 0.0,
          leading: IconButton(
            icon: Icon(Icons.arrow_back, color: Colors.black), onPressed: () {  },
            //onPressed: () =&gt; Navigator.of(context).pop(),
             ),  
         title: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            'LOGIN',
            style: TextStyle(color: Colors.black, fontSize: 16.0),
          ),
          Text(
            'Enter your email and passowrd',
            style: TextStyle(color: Colors.black, fontSize: 14.0),
          )
        ],
      ),
    ],
  ),
  </code></pre>