title: Testing a branch of an existing VS Code extension branch
body: <p>I'm discussing with the developer of an extension in VS Code and I would like to try a pull request that is not ready yet. Unfortunately, I have no idea how to do so. I went in the extension folder under .vscode/extension, I checked out to the modified branch and I used the command "yarn" because that's the package manager it used. What do I need to do to test the new work in progress?</p>
  
  <p>Thank you</p>