Examine source code of Posture!Posture!Posture!

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "description": "Sit up Straight! This extension will help you track your posture as you browse with the help of your webcam.",
  "version": "4.2.1",
  "manifest_version": 2,
  "name": "Posture!Posture!Posture!",
  "options_page": "options.html",
  "background": {
    "scripts": [
      "background.bundle.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon-34.png"
  },
  "icons": {
    "128": "icon-128.png"
  },
  "content_scripts": [
    {
      "run_at": "document_end",
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "contentScript.bundle.js"
      ],
      "css": [
        "content.styles.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "content.styles.css",
    "icon-128.png",
    "icon-34.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e86b185e-b612-4ff7-ae0b-7c9e59e4048b}"
    }
  }
}