Examine source code of Furiganai - Furigana for your WaniKani level

{
  "manifest_version": 3,
  "name": "Furiganai - Furigana for your WaniKani level",
  "short_name": "Furiganai",
  "version": "1.2.0",
  "description": "Adds furigana to pages that lack it, then hides readings for kanji you know via WaniKani. Disabled on WaniKani itself.",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "permissions": [
    "storage",
    "alarms",
    "activeTab"
  ],
  "host_permissions": [
    "https://api.wanikani.com/*"
  ],
  "action": {
    "default_title": "Furiganai",
    "default_popup": "src/popup/index.html",
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "options_ui": {
    "page": "src/options/index.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "exclude_matches": [
        "*://*.wanikani.com/*"
      ],
      "js": [
        "src/content/content-script.js"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "src/background/background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{cd5d4a3d-5a9e-4f2c-a186-ec8ff6b4c51f}",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}