Examine source code of Trestle

{
  "name": "myTrestle Button",
  "version": "1.3.0",
  "description": "Discover the values of your favorite brands",
  "manifest_version": 2,
  "permissions": [
    "tabs",
    "storage"
  ],
  "content_scripts": [
    {
      "run_at": "document_start",
      "match_about_blank": false,
      "all_frames": false,
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "assets/css/fonts.css"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icons/purple-16.png",
    "48": "icons/purple-48.png",
    "128": "icons/purple-128.png"
  },
  "browser_action": {
    "default_icon": {
      "19": "icons/inactive-19.png",
      "38": "icons/inactive-38.png"
    },
    "default_title": "Trestle",
    "browser_style": true
  },
  "web_accessible_resources": [
    "assets/css/fonts.css"
  ],
  "applications": {
    "gecko": {
      "strict_min_version": "52.0"
    }
  }
}