Examine source code of Kronos Timer

{
  "manifest_version": 2,
  "name": "Kronos Timer",
  "version": "1.3.1",
  "description": "Simple tool for tracking your working time.",
  "author": "Nikola Markovic",
  "homepage_url": "https://markovic-nikola.github.io/kronos/",
  "icons": {
    "16": "assets/icon_16.png",
    "32": "assets/icon_32.png",
    "48": "assets/icon_48.png",
    "128": "assets/icon_128.png"
  },
  "browser_action": {
    "default_icon": {
      "16": "assets/icon_16.png",
      "32": "assets/icon_32.png",
      "48": "assets/icon_48.png",
      "128": "assets/icon_128.png"
    },
    "default_title": "Kronos - track your time.",
    "default_popup": "popup/popup.html",
    "browser_style": true
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options/options.html"
  },
  "permissions": [
    "storage",
    "idle"
  ],
  "commands": {
    "play_pause": {
      "suggested_key": {
        "default": "Ctrl+Shift+Space",
        "mac": "Command+Shift+Space"
      },
      "description": "Play/pause timer"
    },
    "stop": {
      "suggested_key": {
        "default": "Ctrl+Shift+Q",
        "mac": "Command+Shift+Q"
      },
      "description": "Stop timer"
    }
  }
}