Examine source code of WaniKani Undo

{
  "name": "WaniKani Undo",
  "description": "Unoficial extension to undo your wrong reviews at Wanikani.",
  "version": "0.2.0",
  "manifest_version": 2,
  "icons": {
    "16": "logo/logo_bb_16x16.png",
    "32": "logo/logo_bb_32x32.png",
    "48": "logo/logo_bb_48x48.png",
    "128": "logo/logo_bb.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.wanikani.com/review/session"
      ],
      "js": [
        "scripts/static.js",
        "scripts/content.js",
        "scripts/kana.js"
      ],
      "css": [
        "styles/content.css"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{227cdb0b-b63f-48be-afb2-b596906430a7}"
    }
  }
}