Examine source code of re-CodeCopy

{
  "manifest_version": 2,
  "name": "re-CodeCopy",
  "description": "Because copy to clipboard buttons should exist on every code snippet",
  "homepage_url": "https://github.com/Staler2019/codecopy",
  "version": "1.4.0",
  "author": "Staler2019",
  "browser_specific_settings": {
    "gecko": {
      "id": "re-codecopy@Staler2019"
    }
  },
  "icons": {
    "16": "images/icon-16.png",
    "48": "images/icon-48.png",
    "128": "images/icon-128.png"
  },
  "browser_action": {
    "default_icon": {
      "16": "images/icon-16.png",
      "48": "images/icon-48.png",
      "128": "images/icon-128.png"
    }
  },
  "permissions": [
    "activeTab"
  ],
  "optional_permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "background": {
    "scripts": [
      "scripts/background.js"
    ]
  },
  "content_scripts": [
    {
      "css": [
        "styles/main.css"
      ],
      "js": [
        "scripts/main.js"
      ],
      "matches": [
        "https://developer.mozilla.org/*",
        "https://medium.com/*",
        "https://www.npmjs.com/*",
        "https://developer.github.com/*",
        "https://stackexchange.com/*",
        "https://*.stackexchange.com/*",
        "https://serverfault.com/*",
        "https://superuser.com/*",
        "https://askubuntu.com/*",
        "https://stackoverflow.com/*",
        "https://www.digitalocean.com/community/*",
        "https://nodejs.org/api/*",
        "https://css-tricks.com/*",
        "https://*.csdn.net/*"
      ]
    }
  ]
}