Examine source code of Waveform Viewer-compare & measure audio

{
  "manifest_version" : 2 ,
  "name" : "Waveform Viewer — compare & measure audio",
  "version" : "1.4.3",
  "description" : "Draw waveforms for any audio on a page. Stack lanes, align onsets, play them together, measure gaps, download clips.",
  "author": "Eric Zhou",
  "homepage_url" : "https://github.com/EricZhou866/waveform-viewer",
  "browser_specific_settings": {
    "gecko": {
      "id": "waveform-viewer@ericzhou866.gmail.com",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  },
  "permissions" : [
    "storage" ,
    "<all_urls>" 
  ],
  "background" : {
    "scripts" : [
      "background.js" 
    ]
  },
  "content_scripts" : [
    {
      "matches" : [
        "<all_urls>" 
      ],
      "js" : [
        "content.js" 
      ],
      "run_at" : "document_start" ,
      "all_frames" : true 
    }
  ],
  "web_accessible_resources" : [
    "page-hook.js"
  ],
  "browser_action" : {
    "default_title" : "Waveform Viewer",
    "default_icon" : {
      "16" : "icons/icon-16.png",
      "32" : "icons/icon-32.png",
      "48" : "icons/icon-48.png",
      "96" : "icons/icon-96.png"
    }
  },
  "icons" : {
    "48" : "icons/icon-48.png",
    "96" : "icons/icon-96.png",
    "128" : "icons/icon-128.png"
  }
}