Examine source code of Don't Visit - Block Sites

{
  "manifest_version": 2,
  "name": "Don't Visit - Block Sites",
  "short_name": "Don't Visit",
  "description": "Blocks you from accessing websites of your choice.",
  "version": "0.7",
  "author": "Christian Sdunek",
  "applications": {
    "gecko": {
      "id": "dontvisit@systemcluster.me",
      "strict_min_version": "57.0"
    }
  },
  "options_ui": {
    "page": "chrome/content/settings_inline.html",
    "open_in_tab": false
  },
  "browser_action": {
    "default_title": "Don't Visit",
    "default_icon": {
      "48": "chrome/skin/icon48.png",
      "64": "chrome/skin/icon64.png",
      "128": "chrome/skin/icon128.png"
    }
  },
  "icons": {
    "48": "chrome/skin/icon48.png",
    "64": "chrome/skin/icon64.png",
    "128": "chrome/skin/icon128.png"
  },
  "background": {
    "scripts": [
      "lib/background.js"
    ],
    "persistent": true
  },
  "web_accessible_resources": [
    "lib/stop.js",
    "lib/stop.css",
    "lib/stop.html",
    "chrome/skin/stop256.png"
  ],
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "activeTab",
    "tabs",
    "storage",
    "*://*/*"
  ]
}