Examine source code of Is Gatsby?

{
  "manifest_version": 2,
  "name": "Is Gatsby?",
  "version": "1.2resigned1",
  "description": "Tell if a page is built using Gatsby",
  "homepage_url": "https://github.com/tsriram/is-gatsby",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png"
  },
  "applications": {
    "gecko": {
      "id": "is-gatsby@tsriram.in"
    }
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "permissions": [
    "file:///*",
    "http://*/*",
    "https://*/*"
  ],
  "page_action": {
    "default_icon": "icons/icon32.png",
    "default_title": "This page doesn't appear to be built with Gatsby :("
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "js/check-gatsby.js"
      ],
      "run_at": "document_end"
    }
  ],
  "author": "Sriram Thiagarajan"
}