Examine source code of ImdbPlay

{
  "manifest_version": 2,
  "name": "Play URL",
  "version": "1.4",
  "description": "Shows a Play button only on IMDB. Works on desktop and Android.",
  "browser_specific_settings": {
    "gecko": {
      "id": "play-url@extension",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "page_action": {
    "default_popup": "popup.html",
    "default_title": "Play"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Play"
  }
}