Examine source code of Page Lock

{
  "manifest_version": 2,
  "name": "Page Lock",
  "version": "1.0.2",
  "description": "Prevents accidental closing of tabs.",
  "icons": {
    "48": "resources/icon1-48.png",
    "96": "resources/icon1-96.png"
  },
  "applications": {
    "gecko": {
      "id": "pagelock@my.manybuddies.com",
      "strict_min_version": "70.0"
    }
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "48": "resources/icon1-48.png",
      "96": "resources/icon1-96.png"
    },
    "default_title": "Page Lock"
  },
  "options_ui": {
    "page": "ui_options/ui_options.html",
    "browser_style": true,
    "open_in_tab": false
  },
  "background": {
    "scripts": [
      "bs_engine.js"
    ]
  },
  "permissions": [
    "<all_urls>",
    "storage",
    "unlimitedStorage",
    "tabs"
  ]
}