Examine source code of Testfully

{
  "manifest_version": 2,
  "version": "1.0.0",
  "name": "Testfully",
  "homepage_url": "https://testfully.io",
  "description": "Testfully's Firefox extension",
  "icons": {
    "16": "/images/testfully_icon_16x16.png",
    "32": "/images/testfully_icon_32x32.png",
    "48": "/images/testfully_icon_48x48.png",
    "64": "images/testfully_icon_64x64.png",
    "128": "/images/testfully_icon_128x128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "applications": {
    "gecko": {
      "id": "@io.testfully"
    }
  }
}