Examine source code of Drag To Go +

{
  "browser_specific_settings": {
    "gecko": {
      "id": "drag-to-go-plus@kuangkuang",
      "strict_min_version": "63.0"
    }
  },
  "manifest_version": 2,
  "name": "Drag To Go +",
  "version": "1.1.2",
  "description": "a firefox plug-in to support multiple drag and drop behavior",
  "icons": {
    "48": "drag-to-go-plus-48.png",
    "96": "drag-to-go-plus-96.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "option.html",
    "open_in_tab": true,
    "browser_style": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js",
        "contentActions.js"
      ]
    }
  ],
  "permissions": [
    "<all_urls>",
    "bookmarks",
    "clipboardWrite",
    "downloads",
    "management",
    "notifications",
    "tabs",
    "search",
    "storage",
    "webNavigation"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'; img-src 'self' data:",
  "web_accessible_resources": [
    "extension.html"
  ]
}