Examine source code of Shortcut Practice

{
  "applications": {
    "gecko": {
      "id": "ryzal@shortcutpractice.com"
    }
  },
  "manifest_version": 2,
  "name": "Shortcut Practice",
  "version": "1.0",
  "description": "Practice and master keyboard shortcuts of your favourite websites and apps",
  "icons": {
    "16": "img/icons/icon.png",
    "48": "img/icons/icon.png",
    "128": "img/icons/icon.png"
  },
  "author": "@ryzalyusoff",
  "homepage_url": "https://shortcutpractice.com",
  "permissions": [
    "tabs",
    "storage",
    "unlimitedStorage"
  ],
  "browser_action": {
    "default_icon": "img/icons/icon.png"
  },
  "background": {
    "persistent": true,
    "scripts": [
      "bg.js"
    ]
  },
  "web_accessible_resources": [
    "js/*",
    "css/*",
    "fonts/*",
    "img/*"
  ],
  "commands": {
    "open_app": {
      "description": "Open the app",
      "suggested_key": {
        "default": "Alt+Shift+K"
      }
    }
  }
}