Examine source code of FurAdder

{
  "author": "Jordan R AW",
  "background": {
    "scripts": [
      "background_scripts/background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/furadder_icon_32.png",
    "default_popup": "popup/furadder.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "crystalsplitter@furadder.net"
    }
  },
  "commands": {
    "open-popup": {
      "description": "Open FurAdder Pop-Up",
      "suggested_key": {
        "default": "Ctrl+Shift+F"
      }
    }
  },
  "content_scripts": [
    {
      "js": [
        "content_scripts/shared_utilities.js"
      ],
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start"
    },
    {
      "js": [
        "content_scripts/twitter_handler.js"
      ],
      "matches": [
        "*://twitter.com/*",
        "*://mobile.twitter.com/*"
      ]
    },
    {
      "js": [
        "content_scripts/furbooru_handler.js"
      ],
      "matches": [
        "*://furbooru.org/*"
      ]
    },
    {
      "js": [
        "content_scripts/derpibooru_handler.js"
      ],
      "matches": [
        "*://derpibooru.org/*"
      ]
    },
    {
      "js": [
        "content_scripts/deviantart_handler.js"
      ],
      "matches": [
        "*://www.deviantart.com/*"
      ]
    },
    {
      "js": [
        "content_scripts/furaffinity_handler.js"
      ],
      "matches": [
        "*://www.furaffinity.net/*"
      ]
    },
    {
      "js": [
        "content_scripts/tumblr_handler.js"
      ],
      "matches": [
        "*://*.tumblr.com/*"
      ]
    },
    {
      "exclude_matches": [
        "*://twitter.com/*",
        "*://mobile.twitter.com/*",
        "*://derpibooru.org/*",
        "*://furbooru.org/*",
        "*://www.deviantart.com/*",
        "*://www.furaffinity.net/*",
        "*://*.tumblr.com/*"
      ],
      "js": [
        "content_scripts/universal_handler.js"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "description": "Allows easy image extraction and uploading to furbooru.org",
  "homepage_url": "https://github.com/CrystalSplitter/Furadder",
  "icons": {
    "32": "icons/furadder_icon_32.png",
    "48": "icons/furadder_icon_48.png"
  },
  "manifest_version": 2,
  "name": "FurAdder",
  "options_ui": {
    "open_in_tab": true,
    "page": "options/options.html"
  },
  "permissions": [
    "<all_urls>",
    "storage",
    "tabs"
  ],
  "version": "1.3.3",
  "web_accessible_resources": [
    "popup/js_src/*"
  ]
}