Examine source code of Media Device Router for Firefox

{
  "manifest_version": 3,
  "name": "Media Device Router for Firefox",
  "version": "3.0.1",
  "description": "Manually route the microphone and speaker used by web apps, remembers preferences per site.",
  "permissions": [
    "storage",
    "scripting",
    "activeTab"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "icons": {
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "action": {
    "default_title": "Media Device Router",
    "default_popup": "popup.html",
    "default_icon": {
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png"
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "bridge.js"
      ],
      "run_at": "document_start",
      "world": "ISOLATED"
    },
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "page-router.js"
      ],
      "run_at": "document_start",
      "world": "MAIN"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "media-device-router@example.local",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}