Examine source code of Jira Extras

{
  "manifest_version": 2,
  "name": "Jira Extras",
  "version": "1.2",
  "default_locale": "en",
  "description": "Jira extras, adds a bunch of features to the Jira UI, like total number of issues.",
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.atlassian.net/jira/projects*"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_end",
      "js": [
        "jquery-3.6.0.min.js",
        "main.js"
      ]
    }
  ]
}