Examine source code of PeekCSS

{
  "manifest_version": 3,
  "name": "PeekCSS",
  "description": "Inspect CSS, colors, fonts, and assets on any webpage.",
  "version": "0.1.4",
  "icons": {
    "16": "/icon/favicon.svg",
    "32": "/icon/favicon.svg",
    "48": "/icon/favicon.svg",
    "96": "/icon/favicon.svg",
    "128": "/icon/favicon.svg"
  },
  "permissions": [
    "storage",
    "activeTab",
    "downloads"
  ],
  "action": {
    "default_icon": "/icon/favicon.svg"
  },
  "host_permissions": [
    "https://fonts.google.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "peekcss@peekcss.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": [
          "authenticationInfo"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "sidebar_action": {
    "default_panel": "sidepanel.html",
    "default_title": "PeekCSS"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}