Examine source code of Tab Switch Keys

{
  "name": "Tab Switch Keys",
  "description": "Keyboard shortcuts for switching tabs (Ctrl+PageUp, Ctrl+PageDown, Ctrl+Tab, Ctrl+Shift+Tab)",
  "manifest_version": 2,
  "version": "2.1resigned1",
  "author": "Alex Vallat",
  "applications": {
    "gecko": {
      "id": "tabswitchkeys@byalexv.co.uk"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "match_about_blank": true
    }
  ]
}