Examine source code of BookWithMatrix plus

{
  "name": "BookWithMatrix",
  "version": "1.0.6",
  "description": "Opens an ITA Matrix itinerary on BookWithMatrix to easily book it. For more information, visit https://bookwithmatrix.com",
  "icons": {
    "32": "assets/icon32.png",
    "48": "assets/icon48.png",
    "64": "assets/icon64.png",
    "128": "assets/icon128.png",
    "256": "assets/icon256.png"
  },
  "browser_action": {
    "default_title": "Open in BookWithMatrix",
    "default_icon": "assets/icon32.png",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://matrix.itasoftware.com/*"
      ],
      "js": [
        "content.js"
      ]
    },
    {
      "matches": [
        "*://bookwithmatrix.com/*"
      ],
      "js": [
        "installed.js"
      ]
    }
  ],
  "permissions": [
    "https://bookwithmatrix.com/",
    "activeTab",
    "tabs"
  ],
  "web_accessible_resources": [
    "assets/icon32.png",
    "assets/icon48.png",
    "assets/icon64.png",
    "assets/icon128.png",
    "assets/icon256.png",
    "popup.html",
    "content.js",
    "installed.js"
  ],
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{f0dd0f62-774f-4a5c-8510-66f495aefe36}"
    }
  }
}