Examine source code of Xdebug Button

{
  "manifest_version": 2,
  "name": "Xdebug Button",
  "version": "0.3.0",
  "description": "",
  "homepage_url": "https://github.com/bash/xdebug-webextension",
  "permissions": [
    "tabs",
    "cookies",
    "storage",
    "<all_urls>"
  ],
  "icons": {
    "128": "icons/icon.svg"
  },
  "page_action": {
    "default_icon": "icons/icon.svg",
    "default_title": "Enable Xdebug"
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "js": [
        "content.js"
      ]
    }
  ],
  "default_locale": "en",
  "applications": {
    "gecko": {
      "id": "xdebug-button@rubys.ninja"
    }
  }
}