Examine source code of Feedbin Subscribe & Save

{
  "manifest_version": 3,
  "name": "Feedbin",
  "version": "1.8",
  "description": "Subscribe to feeds and save pages to Feedbin.",
  "icons": {
    "32": "assets/images/icon-square-32.png",
    "64": "assets/images/icon-square-64.png"
  },
  "permissions": [
    "activeTab",
    "scripting",
    "storage"
  ],
  "action": {
    "default_popup": "index.html",
    "default_title": "Feedbin"
  },
  "commands": {
    "_execute_action": {
      "description": "Open the extension",
      "suggested_key": {
        "default": "Ctrl+Shift+F",
        "mac": "MacCtrl+Shift+F"
      }
    },
    "open_in_background": {
      "description": "Open current article in a background tab",
      "suggested_key": {
        "default": "Ctrl+Shift+V",
        "mac": "MacCtrl+Shift+V",
        "linux": "Ctrl+Shift+U"
      }
    }
  },
  "background": {
    "scripts": [
      "assets/javascript/content/worker.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "support@feedbin.com",
      "strict_min_version": "128.0"
    }
  }
}