title: Write initial settings to settings.json
body: <p>I am looking for a way to write initial settings to settings.json for when my extension is installed.</p>
  
  <p>I found WorkspaceConfiguration API, but that seems to retrieving/updating values at runtime.</p>
  
  <p>I'm looking to get my settings + comments into the default settings file</p>
  
  <p>e.g. How TSLint does it:
  <a href="https://i.stack.imgur.com/hO0kk.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hO0kk.png" alt="enter image description here"></a></p>