Examine source code of Reasonable Typography

{
  "description": "sets reasonable defaults for web typography",
  "manifest_version": 2,
  "name": "Reasonable Typography",
  "version": "1.0",
  "homepage_url": "https://github.com/fraction/reasonable-typography",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "index.js"
      ]
    }
  ]
}