Examine source code of HTTP Border

{
  "description": "Adds a visible top border to any websites without HTTPS. You can close it by pressing the close button.",
  "manifest_version": 2,
  "name": "HTTP Border",
  "version": "1.3resigned1",
  "homepage_url": "https://github.com/FrancoBarppG/http-border",
  "icons": {
    "48": "images/icons/icon-48.png",
    "96": "images/icons/icon-96.png"
  },
  "web_accessible_resources": [
    "images/pagewarning.png",
    "images/closebutton.png"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://*/*"
      ],
      "js": [
        "httpborder.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{581b1446-c419-4b22-9709-325f7ddcd786}"
    }
  }
}