title: Expand The App bar in Flutter to Allow Multi-Line Title?
body: <p>Does anyone know how I can create an app bar with a multi-line title, as per the material guidelines show here? </p>
  
  <p><a href="https://material.io/design/components/app-bars-top.html#anatomy" rel="noreferrer">https://material.io/design/components/app-bars-top.html#anatomy</a></p>
  
  <p><a href="https://i.stack.imgur.com/mCokC.png" rel="noreferrer"><img src="https://i.stack.imgur.com/mCokC.png" alt="Multi-line app bar"></a></p>
  
  <p>Any ideas how to do this? It seems like it should be straightforward given that it's part of the material guidelines! Worth pointing out that the title is user defined, so I want to allow the app bar to expand from a single line to multiple lines (perhaps with a limit imposed) depending on user input.</p>
  
  <p>Mike</p>