Examine source code of Morqana auto refresh

{
  "manifest_version": 2,
  "name": "Morqana auto refresh",
  "version": "1.7.0",
  "description": "Simple and reliable auto-refresh extension for Firefox",
  "permissions": [
    "tabs",
    "activeTab",
    "storage",
    "<all_urls>",
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "background-simple.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-simple.js"
      ],
      "run_at": "document_end",
      "all_frames": false
    }
  ],
  "options_ui": {
    "page": "options-simple.html",
    "open_in_tab": true
  },
  "browser_action": {
    "default_title": "Morqana auto refresh Settings",
    "default_popup": "options-simple.html"
  },
  "web_accessible_resources": [
    "debug-simple.html"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "simple-auto-refresh@firefox-extension.com",
      "strict_min_version": "58.0"
    }
  }
}