Examine source code of Focus Interval Tone

{
  "manifest_version": 2,
  "name": "Focus Interval Tone",
  "version": "1.0",
  "description": "Minimal focus timer using short music tones instead of loud alarms.",
  "permissions": [
    "alarms"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Focus Interval Tone",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "focus-interval-tone@amo.local",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}