Examine source code of Heartstopper

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Heartstopper",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center bottom"
      ],
      "additional_backgrounds_tiling": [
        "repeat-x"
      ]
    },
    "colors": {
      "toolbar": "rgb(242, 255, 67)",
      "toolbar_text": "rgb(87, 141, 247)",
      "frame": "rgb(87, 141, 247)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(29, 96, 230)",
      "toolbar_field_text": "rgb(242, 255, 67)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(87, 141, 247)",
      "popup_text": "rgb(242, 255, 67)",
      "tab_loading": "rgb(255, 255, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{25a9bdf9-698e-4141-9ece-690011e89d20}"
    }
  }
}