Examine source code of silksong SoS

{
  "manifest_version": 2,
  "version": "1.2",
  "name": "silksong SoS",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(2, 2, 4, 0)",
      "toolbar_text": "rgb(213, 154, 103)",
      "frame": "rgb(2, 2, 4)",
      "tab_background_text": "rgb(213, 154, 103)",
      "toolbar_field": "rgba(2, 2, 4, 0.5)",
      "toolbar_field_text": "rgb(230, 193, 163)",
      "tab_line": "rgb(213, 154, 103)",
      "popup": "rgba(2, 2, 4, 0.95)",
      "popup_text": "rgb(230, 193, 163)",
      "sidebar_border": "rgb(0, 43, 46)",
      "sidebar_highlight": "rgb(230, 193, 163)",
      "sidebar": "rgb(2, 2, 4)",
      "tab_loading": "rgb(213, 153, 103)",
      "tab_selected": "rgb(0, 43, 46)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{312bd1b7-2252-4a4f-b47e-ad9b30a00233}"
    }
  }
}