title: No error highlighting for a F# file named test.fsx in VSCode
body: <p>When I open test.fsx in VSCode, it doesn't show error highlighting. If I change its name to Test.fsx or test1.fsx, it works fine. Does test.fsx have special meaning in F# project? </p>
  
  <p>I created F# project file using <code>dotnet new console --language F#</code> and added test.fsx under root folder.</p>
  
  <ul>
  <li>VSCode: 1.45.1 </li>
  <li>Ionide: 4.11.1</li>
  </ul>
  
  <p>Both are latest version.</p>
  
  <p>I also have Visual Studio for Mac installed, but it doesn't have such problem.</p>