Examine source code of DuolingoFurigana

{
  "manifest_version": 2,
  "name": "DuolingoFurigana",
  "description": "Extension to add Furigana to Duolingo's Kanji.",
  "version": "0.2.3resigned1",
  "icons": {
    "128": "icon128.png",
    "256": "icon256.png"
  },
  "browser_action": {
    "default_icon": "icon128.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage",
    "tabs",
    "*://www.duolingo.com/practice",
    "*://www.duolingo.com/skill/*"
  ],
  "content_scripts": [
    {
      "run_at": "document_end",
      "matches": [
        "*://www.duolingo.com/*"
      ],
      "js": [
        "jquery.min.js",
        "kuroshiro.js",
        "main.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "dict/base.dat.gz",
    "dict/cc.dat.gz",
    "dict/check.dat.gz",
    "dict/tid.dat.gz",
    "dict/tid_map.dat.gz",
    "dict/tid_pos.dat.gz",
    "dict/unk.dat.gz",
    "dict/unk_char.dat.gz",
    "dict/unk_compat.dat.gz",
    "dict/unk_invoke.dat.gz",
    "dict/unk_map.dat.gz",
    "dict/unk_pos.dat.gz"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ef9ede87-addc-4cd6-9052-cd720525b03b}"
    }
  }
}