Examine source code of DuckDuckGo Date Range

{
  "manifest_version": 2,
  "name": "DuckDuckGo Date Range",
  "version": "1.1",
  "description": "User can permanently select a date range for DuckDuckGo searches",
  "icons": {
    "128": "icon128.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "https://duckduckgo.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icon128.png",
    "default_popup": "popup_options.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{89f5ad34-5eb9-4378-97f6-b26ec8f31e36}"
    }
  }
}