Examine source code of Proton Promo Hider

{
  "manifest_version": 2,
  "name": "Proton Promo Hider",
  "version": "1.0",
  "description": "Hides promotional messages and special offer buttons in Proton Mail/Drive/Calendar.",
  "content_scripts": [
    {
      "matches": [
        "*://*.proton.me/*",
        "*://*.protonmail.com/*"
      ],
      "css": [
        "hide-promos.css"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {
    "48": "icon.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "proton-promo-hider@local",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}