Examine source code of Imgsed

{
  "name": "Imgsed",
  "description": "View Instagram without an account.",
  "version": "3.5",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko_android": {},
    "gecko": {
      "id": "{4c62644f-fc4b-4d44-8b51-12f3fb7423b2}"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "256": "imgsed.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://*.instagram.com/*"
  ]
}