title: Surrounding color for the label text in Text Field
body: <p>can anyone please help me with this</p>
  <p>this is my code below</p>
  <pre><code>TextField(
      decoration: InputDecoration(
          filled: true,
          fillColor: Colors.white,
          focusedBorder: OutlineInputBorder(
            borderRadius:
                BorderRadius.all(Radius.circular(13)),
            borderSide: BorderSide(
                color: Colors.white,
                width: 2,
                style: BorderStyle.solid),
          ),
          border: OutlineInputBorder(),
          labelText: 'Username',
          labelStyle: TextStyle(
            color: Colors.black,
            fontSize: 20,
          ),
          hintText: 'Enter Name Here',
          hintStyle: TextStyle(
            color: Colors.black,
          )),
    )
  </code></pre>
  <p>Here you have the screenshot of my requirement:
  <a href="https://i.stack.imgur.com/SW2ZL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SW2ZL.png" alt="enter image description here" /></a></p>