Examine source code of Midnightify

{
  "manifest_version": 2,
  "version": "0.0.1",
  "name": "Midnightify",
  "icons": {
    "48": "midnight-icon.gif",
    "96": "midnight-icon.gif"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "main.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "midnight.gif"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3b2a115d-16b7-414d-adad-e2b4c023f158}"
    }
  }
}