Examine source code of Waifu Image Replacer

{
  "manifest_version": 2,
  "name": "Random Image Replacer",
  "version": "1.0.1",
  "description": "Replace images with random images from an API",
  "permissions": [
    "menus",
    "activeTab",
    "tabs",
    "storage",
    "https://api.waifu.im/*",
    "https://cdn.waifu.im/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "random-image-replacer@example.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}