Examine source code of IMFD

{
  "manifest_version": 2,
  "name": "IMFD",
  "version": "0.0.2",
  "description": "Adds IMDb link to CSFD movie pages.",
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "js": [
        "content.js"
      ],
      "matches": [
        "https://www.csfd.cz/film/*"
      ]
    }
  ],
  "permissions": [
    "https://www.csfd.cz/film/*",
    "https://vychopen.org/imfd/json/*"
  ]
}