Examine source code of Leave A Trace

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Leave A Trace Reminder",
  "description": "This extension reminds users to visit leaveatrace.co at relevant times",
  "version": "1.4resigned1",
  "icons": {
    "16": "LAT_16.png",
    "48": "LAT_48.png",
    "128": "LAT_128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.kayak.com/*",
        "*://*.priceline.com/*",
        "*://*.expedia.com/*",
        "*://*.expedia.ca/*",
        "*://*.amazon.com/*",
        "*://*.amazon.ca/*",
        "*://*.hotwire.com/*",
        "*://*.agoda.com/*",
        "*://*.spg.com/*",
        "*://*.hostelbookers.com/*",
        "*://*.hostelworld.com/*",
        "*://*.hotelscombined.com/*",
        "*://*.booking.com/*",
        "*://*.google.com/flights/*",
        "*://*.google.ca/flights/*",
        "*://*.aircanada.com/*",
        "*://*.delta.com/*",
        "*://*.united.com/*",
        "*://*.aa.com/*",
        "*://*.skyscanner.com/*",
        "*://*.skyscanner.ca/*"
      ],
      "js": [
        "script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_action": {
    "default_title": "Leave A Trace",
    "default_icon": "LAT_16.png",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "storage"
  ],
  "gecko": {
    "id": "firefoxreminder@leaveatrace.co",
    "strict_min_version": "42.0",
    "strict_max_version": "50.*"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{69569bcf-6fc3-4b05-9eca-3118dfb83368}"
    }
  }
}