Examine source code of FuriHover

{
  "manifest_version": 2,
  "name": "FuriHover",
  "version": "1.0",
  "description": "Hides furigana until the associated word is moused over.",
  "icons": {
    "48": "icons/hover-48.png",
    "96": "icons/hover-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "style.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{cdf43b4a-31d3-4a9d-825f-40394e062ae2}"
    }
  }
}