VS Code Extension: Add a snippet for the special Quarto comment that indicates layers in SCSS files

[cwickham]

Something like, scss.json:

{
  "Layer section": {
    "prefix": "layer",
    "body": [
      "/*-- scss:${1|defaults,rules,uses,functions,mixins|} --*/",
      "",
      "$2"
    ],
    "description": "Add comment to denote Quarto SCSS layer"
  }
}