Examine source code of BGG Previewer

{
  "name": "BGG Previewer",
  "description": "Get key details about a board game, in-situ, by hovering over a link to a BGG game page.",
  "manifest_version": 2,
  "version": "1.0.2",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.boardgamegeek.com/*"
      ],
      "js": [
        "bgg-page.js"
      ],
      "css": [
        "bgg-page.css"
      ],
      "all_frames": true
    }
  ],
  "web_accessible_resources": [
    "frame.js",
    "frame.html",
    "frame.css"
  ],
  "permissions": [
    "https://api.geekdo.com/*"
  ]
}