Examine source code of Roll20 Role Selection

{
  "name": "Roll20 Role Selection",
  "manifest_version": 2,
  "version": "1.0",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "https://app.roll20.net/editor/setcampaign/*"
  ],
  "background": {
    "scripts": [
      "redirect.js"
    ]
  },
  "icons": {
    "128": "icon128.png"
  }
}