Examine source code of Better jump to tab

{
  "manifest_version": 2,
  "name": "Better jump to tab",
  "version": "1.1resigned1",
  "description": "Jump to tabs with Ctrl+#. Ctrl+9 jumps to your last tab, and Ctrl+8 jumps to your first non-pinned tab.",
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "selectTab1": {
      "suggested_key": {
        "default": "Ctrl+1"
      },
      "description": "Activate Tab 1"
    },
    "selectTab2": {
      "suggested_key": {
        "default": "Ctrl+2"
      },
      "description": "Activate Tab 2"
    },
    "selectTab3": {
      "suggested_key": {
        "default": "Ctrl+3"
      },
      "description": "Activate Tab 3"
    },
    "selectTab4": {
      "suggested_key": {
        "default": "Ctrl+4"
      },
      "description": "Activate Tab 4"
    },
    "selectTab5": {
      "suggested_key": {
        "default": "Ctrl+5"
      },
      "description": "Activate Tab 5"
    },
    "selectTab6": {
      "suggested_key": {
        "default": "Ctrl+6"
      },
      "description": "Activate Tab 6"
    },
    "selectTab7": {
      "suggested_key": {
        "default": "Ctrl+7"
      },
      "description": "Activate Tab 7"
    },
    "selectTab8": {
      "suggested_key": {
        "default": "Ctrl+8"
      },
      "description": "Activate First Non-pinned Tab"
    },
    "selectTab9": {
      "suggested_key": {
        "default": "Ctrl+9"
      },
      "description": "Activate Last Tab"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e97a4d1c-4f20-457d-8f4b-473790665413}"
    }
  }
}