Examine source code of Sound Level Meter

{
  "manifest_version": 2,
  "version": "0.1.0",
  "name": "Sound Level Meter",
  "description": "shows a graph and sound's decibel values (min/avg/max) by measuring the environmental noise",
  "permissions": [
    "storage",
    "contextMenus"
  ],
  "offline_enabled": true,
  "icons": {
    "16": "data/icons/16.png",
    "32": "data/icons/32.png",
    "48": "data/icons/48.png",
    "64": "data/icons/64.png",
    "128": "data/icons/128.png",
    "256": "data/icons/256.png",
    "512": "data/icons/512.png"
  },
  "background": {
    "persistent": false,
    "scripts": [
      "background.js"
    ]
  },
  "homepage_url": "https://add0n.com/sound-level-meter.html",
  "browser_action": {}
}