Examine source code of ForwardMail Extension

{
  "manifest_version": 2,
  "name": "ForwardMail Extension",
  "version": "3.2.0",
  "icons": {
    "16": "static/icons/favicon-16.png",
    "32": "static/icons/favicon-32.png",
    "48": "static/icons/favicon-48.png",
    "128": "static/icons/favicon-128.png"
  },
  "description": "Protect your email address.",
  "homepage_url": "https://forwardmail.rocks",
  "short_name": "ForwardMail",
  "permissions": [
    "activeTab",
    "storage",
    "clipboardWrite",
    "https://forwardmail.herokuapp.com/*",
    "https://forwardmail.rocks/*",
    "http://localhost:8080/*"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "author": "stephancill",
  "applications": {
    "gecko": {
      "id": "addon@forwardmail.rocks"
    }
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "static/icons/favicon-16.png",
      "32": "static/icons/favicon-32.png",
      "48": "static/icons/favicon-48.png",
      "128": "static/icons/favicon-128.png"
    },
    "default_title": "ForwardMail",
    "browser_style": false
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "http://localhost:8080/accounts/login/extension",
        "https://forwardmail.rocks/accounts/login/extension",
        "https://forwardmail.herokuapp.com/accounts/login/extension"
      ],
      "js": [
        "js/contentScript.bundle.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "js/background.bundle.js"
    ]
  }
}