Examine source code of Find elements diff

{
  "manifest_version": 2,
  "name": "Find elements diff",
  "description": "Take screenshots of elements and compare images",
  "version": "0.0.1",
  "devtools_page": "devtools.html",
  "browser_action": {
    "default_icon": "icon.png"
  },
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "background": {
    "scripts": [
      "build/background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "build/content.js"
      ]
    }
  ],
  "permissions": [
    "<all_urls>"
  ]
}