Examine source code of Tab Navigator

{
  "manifest_version": 2,
  "name": "Tab Navigator",
  "version": "1.0.0",
  "description": "Navigate through tab history using keyboard shortcuts. Press Ctrl+Alt+Left to go back and Ctrl+Alt+Right to go forward through your previously visited tabs.",
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-navigator-ext@alexlv.com",
      "strict_min_version": "58.0"
    }
  },
  "license": "MIT",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "navigate-back": {
      "suggested_key": {
        "default": "Ctrl+Alt+Left"
      },
      "description": "Navigate to previous tab in history"
    },
    "navigate-forward": {
      "suggested_key": {
        "default": "Ctrl+Alt+Right"
      },
      "description": "Navigate to next tab in history"
    }
  }
}