Examine source code of Quick Maths

{
  "name": "Quick Maths",
  "version": "1.4",
  "description": "A persistent tiny calculator for quick maths!",
  "manifest_version": 2,
  "background": {
    "scripts": [
      "src/background.js"
    ],
    "persistent": false
  },
  "web_accessible_resources": [
    "src/popup.html"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "src/load.js"
      ],
      "run_at": "document_end"
    }
  ],
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "windows": "Alt+Shift+M",
        "mac": "Alt+Shift+M",
        "chromeos": "Alt+Shift+M",
        "linux": "Alt+Shift+M"
      }
    }
  },
  "icons": {
    "128": "static/icon128.png"
  },
  "browser_action": {
    "default_icon": "static/icon.png",
    "default_title": "Quick Maths"
  },
  "permissions": [
    "https://api.gumroad.com/v2/licenses/verify",
    "storage",
    "<all_urls>",
    "activeTab"
  ]
}