Examine source code of MakeItSnow

{
  "manifest_version": 2,
  "name": "Snowfall Plugin",
  "version": "1.0",
  "description": "Adds a snowfall effect to webpages with interactive snowflakes.",
  "permissions": [
    "storage",
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/snowflake.webp",
    "default_title": "Snowfall Plugin",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "snow.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "snowfall@westberg.dev"
    }
  },
  "web_accessible_resources": [
    "assets/jingle.mp3"
  ]
}