Examine source code of Number Dectection

{
  "manifest_version": 2,
  "name": "horizon number detection",
  "version": "1.3",
  "description": "Number detection",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "all_frames": true
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{08166c3c-8567-486f-9cba-0dfdef26dc32}"
    }
  }
}