Examine source code of Canvas painted cave

{
  "theme": {
    "images": {
      "theme_frame": "Canvaspaintedcave.jpg"
    },
    "colors": {
      "frame": "#5333de",
      "tab_background_text": "#21ada6"
    }
  },
  "version": "2.0",
  "name": "Canvas painted cave",
  "manifest_version": 2,
  "description": "Caves painted with light and darkness for depth. As if you are standing inside looking out."
}