Examine source code of Procrastination Killer

{
  "manifest_version": 2,
  "name": "Procrastination Killer",
  "version": "1.0",
  "description": "Removes recommended videos from YouTube. (Literally just runs document.getElementById(\"secondary\").remove(); on any link with youtube.com/watch in it)",
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/watch*"
      ],
      "js": [
        "pkill.js"
      ]
    }
  ]
}