Examine source code of Website Blocker

{
  "name": "Website Blocker",
  "version": "1.0",
  "manifest_version": 2,
  "description": "Blocks specified websites from Carlo Westarp.",
  "author": "Carlo Westarp",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1d2d6451-e4f9-4d9e-a625-8e09316a109b}"
    }
  }
}