Examine source code of DOI Helper

{
  "manifest_version": 2,
  "name": "DOI Helper",
  "version": "1.0.2.1",
  "description": "A little add-on appending SciHub buttons for some webpages with s c i e n c e.",
  "icons": {
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://inspirehep.net/*"
      ],
      "js": [
        "inspire-hep.js"
      ]
    },
    {
      "matches": [
        "*://*.sciencedirect.com/*"
      ],
      "js": [
        "science-direct.js"
      ]
    },
    {
      "matches": [
        "*://science.sciencemag.org/*"
      ],
      "js": [
        "science.js"
      ]
    },
    {
      "matches": [
        "*://journals.aps.org/*/abstract/*"
      ],
      "js": [
        "aps.js"
      ]
    }
  ]
}