message: Add `experimental.useAtlasEngine` to schema
  does what it says on the can.
  * [x] closes
diff: "description": "Use to set a path to a pixel shader to use with the Terminal. Overrides `experimental.retroTerminalEffect`. This is an experimental feature, and its continued existence is not guaranteed.",
  "type": "string"
  },
  + "experimental.useAtlasEngine": {
  + "description": "Enable using the experimental new rendering engine for this profile. This is an experimental feature, and its continued existence is not guaranteed.",
  + "type": "boolean",
  + "default": false
  + },
  "fontFace": {
  "default": "Cascadia Mono",
  "description": "[deprecated] Define 'face' within the 'font' object instead.",
  