Examine source code of Better Newgrounds Feed

{
  "description": "An extension which embeds full size artwork directly into the social feed on Newgrounds.",
  "manifest_version": 2,
  "name": "Better Newgrounds Feed",
  "version": "1.4.1",
  "icons": {
    "16": "BNGF-16.png",
    "48": "BNGF-48.png",
    "128": "BNGF-128.png"
  },
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://www.newgrounds.com/social*"
      ],
      "js": [
        "jquery-3.4.1.js",
        "contentScript.js"
      ],
      "run_at": "document_end"
    }
  ]
}