Examine source code of Discord Attachment Viewer

{
  "manifest_version": 2,
  "name": "Discord Attachment Viewer",
  "description": "View uploaded content without downloading it",
  "version": "1.0.3",
  "permissions": [
    "https://cdn.discordapp.com/attachments/*",
    "https://media.discordapp.net/attachments/*",
    "webRequestBlocking",
    "webRequest"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{89863541-5d0c-4e7b-bbda-51f5a139fc36}"
    }
  }
}