Examine source code of NetMeter Web

{
  "manifest_version": 2,
  "name": "NetMeter Web",
  "version": "0.0.1.3",
  "description": "Web Data Consumption Monitor Extension: Stay Informed About Site Bandwidth Usage",
  "icons": {
    "128": "public/icon-128.png"
  },
  "web_accessible_resources": [
    "public/icon-128.png",
    "public/icon-34.png",
    "popup/index.html",
    "background/index.js",
    "content/index.js",
    "assets/*"
  ],
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "storage",
    "tabs",
    "https://*/*",
    "http://*/*",
    "ws://*/*",
    "wss://*/*"
  ],
  "background": {
    "scripts": [
      "background/index.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup/index.html",
    "default_icon": "public/icon-34.png"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*",
        "<all_urls>"
      ],
      "js": [
        "content/index.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2b388627-4c28-4933-aa30-ade03f16a8ee}"
    }
  }
}