Examine source code of Phone Number Beautifier

{
  "manifest_version": 2,
  "name": "Phone Number Beautifier",
  "description": "Formats phone numbers with dashes to make them easier to read",
  "version": "0.3.1",
  "homepage_url": "https://github.com/own3mall/Phone-Number-Beautifier",
  "icons": {
    "64": "icons/phone_number_beautifier.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "phone-beautifier-toolbar-button-clicked.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "64": "icons/phone_number_beautifier.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "js": [
        "phone-beautifier.js"
      ]
    }
  ]
}