Examine source code of Asset Drop

{
  "manifest_version": 2,
  "name": "Asset Drop",
  "description": "Download game assets directly into your project folder.",
  "version": "0.1.4",
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "permissions": [
    "nativeMessaging",
    "downloads",
    "storage",
    "*://*.itch.io/*",
    "*://itch.io/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "asset-drop@assetdrop.io",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "sidebar_action": {
    "default_panel": "sidepanel.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.itch.io/*"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}