Examine source code of NoClickjack

{
  "manifest_version": 2,
  "name": "NoClickjack",
  "version": "2019.10.3.3",
  "description": "Shows clickjack attempts and displays CryptoColor® indicator when enabled",
  "icons": {
    "96": "Icons/MainIcon.png"
  },
  "developer": {
    "name": "StrikeForce Technologies, Inc.",
    "url": "https://www.strikeforcetech.com/"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_title": "NoClickjack",
    "default_popup": "popup.html",
    "default_icon": "Icons/MainIcon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*",
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "content.js"
      ],
      "all_frames": true
    }
  ],
  "permissions": [
    "tabs",
    "*://*/*",
    "http://*/*",
    "https://*/*"
  ]
}