Examine source code of Get Element Id

{
  "manifest_version": 2,
  "name": "Get Element Id",
  "version": "1.0",
  "permissions": [
    "contextMenus",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_script.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{dcf67831-d65e-4d09-bde3-0e9934f1435f}"
    }
  }
}