title: how to force order in vscode extension CompletionItems
body: <p>I am writing a custom VSCode Extension that helps me add relative (from the workspace) links to files in my project; I have two use cases:</p>
  
  <p>1) search for files by keyword (searches anywhere in the workspace)
  2) list files by folder</p>
  
  <p>Since "list files by folder" is more specific, and thus more likely to contain the desired, I want them to show up first in the CompletionItem suggestions.</p>
  
  <p>So when I search for "pictures", i get a list of CompletionItems</p>
  
  <pre><code>../../../../animals/pictures/cat.png (by keyword)
  ../../../../animals/pictures/dog.png (by keyword)
  ../../../pets/pictures/dog.png (by keyword)
  ./pictures/dog.png (by files in folder)
  </code></pre>
  
  <p>I can add the CompletionItems to the return array in any order I like, and it still lists alphabetically.</p>
  
  <p>Is there any way I can control the order the results list?</p>