Examine source code of NFSW Holder

{
  "manifest_version": 2,
  "name": "NFSW Holder",
  "version": "1.3",
  "description": "Switch any website image with NSFW image",
  "icons": {
    "48": "icons/app-icon.svg"
  },
  "permissions": [
    "tabs",
    "cookies",
    "<all_urls>"
  ],
  "web_accessible_resources": [
    "popup/images/hunkholder.png",
    "popup/images/babeholder.png"
  ],
  "browser_action": {
    "default_icon": "icons/app-icon.svg",
    "theme_icons": [
      {
        "light": "icons/app-icon-light.svg",
        "dark": "icons/app-icon.svg",
        "size": 32
      }
    ],
    "default_title": "NSFW Holder",
    "default_popup": "popup/popup.html"
  },
  "background": {
    "scripts": [
      "background_scripts/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_scripts/update.js"
      ]
    }
  ]
}