Examine source code of ModWe

{
  "manifest_version": 2,
  "applications": {
    "gecko": {
      "id": "modwe@tomas-chyly.com"
    }
  },
  "name": "ModWe",
  "version": "1.2.0",
  "description": "Modify websites using custom CSS and JS snippets.",
  "icons": {
    "48": "icons/ic_dashboard_48dp_1x.png",
    "96": "icons/ic_dashboard_48dp_2x.png"
  },
  "permissions": [
    "<all_urls>",
    "storage",
    "activeTab",
    "tabs",
    "downloads"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/ic_dashboard_48dp_1x.png",
    "default_title": "ModWe",
    "default_popup": "popup/default.html"
  },
  "options_ui": {
    "page": "options/default.html",
    "browser_style": true,
    "open_in_tab": true
  }
}