Examine source code of AudioReporter

{
  "browser_specific_settings": {
    "gecko": {
      "id": "audioreporter@m4ym4y.github.io",
      "strict_min_version": "42.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "description": "Posts URL currently playing audio to a local server",
  "manifest_version": 2,
  "name": "AudioReporter",
  "permissions": [
    "tabs"
  ],
  "version": "0.2"
}