Examine source code of injectooor

{
  "manifest_version": 2,
  "name": "injectooor",
  "version": "1.5",
  "description": "A minimalistic Firefox extension to inject custom JavaScript into specified URLs.",
  "permissions": [
    "storage",
    "tabs",
    "<all_urls>",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "19": "icon-19.png",
      "38": "icon-38.png"
    }
  },
  "options_ui": {
    "page": "settings.html",
    "open_in_tab": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "48": "icon-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{531480d4-0398-499e-bdfc-79e7d6cf0055}"
    }
  }
}