Examine source code of Watch it-!

{
  "name": "Watch it!",
  "description": "Right click and Watch it!",
  "version": "0.2.0",
  "manifest_version": 2,
  "homepage_url": "https://github.com/Raayib",
  "icons": {
    "32": "icons/32.png",
    "64": "icons/64.png",
    "128": "icons/128.png"
  },
  "browser_action": {
    "default_icon": "icons/128.png",
    "default_title": "Watch it!"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "contextMenus",
    "storage",
    "*://*/*"
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{31688f72-3642-415b-9243-dacfbff18f6e}",
      "strict_min_version": "57.0"
    }
  }
}