Examine source code of Simple URL Navigator

{
  "manifest_version": 2,
  "name": "Simple URL Navigator",
  "version": "1.0",
  "description": "Increment or decrement an integer in the URL with keyboard shortcuts.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "background": {
    "scripts": [
      "popup.js"
    ],
    "persistent": false
  },
  "commands": {
    "increment-url": {
      "suggested_key": {
        "default": "Ctrl+Shift+Up"
      },
      "description": "Increment the integer in the URL"
    },
    "decrement-url": {
      "suggested_key": {
        "default": "Ctrl+Shift+Down"
      },
      "description": "Decrement the integer in the URL"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ef4bcf4e-cb72-4769-9b40-663e659da614}"
    }
  }
}