Examine source code of ECS:R+

{
  "manifest_version": 3,
  "name": "ECS:R+",
  "version": "2.3",
  "description": "ECS:R QoL+",
  "browser_specific_settings": {
    "gecko": {
      "id": "solimons-extension@yourdomain.com",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "on_install": false,
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "imgs/icon16.png",
    "48": "imgs/icon48.png",
    "128": "imgs/icon128.png"
  },
  "permissions": [
    "notifications",
    "storage"
  ],
  "host_permissions": [
    "https://ecsr.io/*",
    "https://ecomons.ecsr.io/*"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "imgs/*.jpg",
        "imgs/*.png",
        "imgs/*.svg"
      ],
      "matches": [
        "https://ecomons.ecsr.io/*"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://ecsr.io/*",
        "https://ecomons.ecsr.io/user/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ]
}