Examine source code of FileWatcher

{
  "description": "Reload a web page when one of the watched local filesystem items changes.",
  "manifest_version": 2,
  "name": "FileWatcher",
  "version": "1.2.1",
  "homepage_url": "https://coolsoft.altervista.org/filewatcher",
  "browser_specific_settings": {
    "gecko": {
      "id": "filewatcher@coolsoft.altervista.org",
      "strict_min_version": "60.0"
    }
  },
  "permissions": [
    "tabs",
    "nativeMessaging",
    "notifications",
    "storage"
  ],
  "icons": {
    "32": "icons/icon-32.png"
  },
  "background": {
    "scripts": [
      "js/common.js",
      "background/background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "32": "icons/icon-32-off.png"
    },
    "default_popup": "popup/popup.html"
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true,
    "chrome_style": true
  },
  "web_accessible_resources": [
    "help/*"
  ]
}