Examine source code of Hex Preview

{
  "manifest_version": 2,
  "name": "HexPreview",
  "description": "Allows you to preview any Hex colour code in a little box, by highlighting it.",
  "version": "1.2.2",
  "developer": {
    "name": "Lucy Havok"
  },
  "homepage_url": "https://code.naln1.ca/HexPreview",
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "options_ui": {
    "page": "settings/settings.html"
  },
  "browser_action": {
    "default_popup": "settings/settings.html"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "preview.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "HexPreview@naln1.ca"
    }
  }
}