Examine source code of GitHub - Branch Scroll

{
  "manifest_version": 2,
  "name": "GitHub - Branch Scroll",
  "version": "0.2resigned1",
  "description": "Keeps branch info on the right side of the screen when scrolling through a PR",
  "content_scripts": [
    {
      "matches": [
        "*://*.github.com/*/*/pull/*"
      ],
      "js": [
        "jquery-3.3.1.min.js",
        "branchscroll.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3c1380bc-7e56-44fc-a5f1-23967324e375}"
    }
  }
}