Examine source code of tabs-shortcuts

{
  "manifest_version": 2,
  "name": "shortcuts",
  "version": "1.1.0",
  "description": "Tab Shortcuts",
  "permissions": [
    "tabs",
    "activeTab",
    "webNavigation"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@tabshorcutpermission",
      "data_collection_permissions": {
        "required": [
          "browsingActivity",
          "websiteActivity"
        ],
        "optional": []
      }
    }
  },
  "icons": {
    "72": "icon/icon.png"
  },
  "commands": {
    "first_tab": {
      "suggested_key": {
        "default": "Ctrl+1"
      }
    },
    "second_tab": {
      "suggested_key": {
        "default": "Ctrl+2"
      }
    },
    "third_tab": {
      "suggested_key": {
        "default": "Ctrl+3"
      }
    },
    "fouth_tab": {
      "suggested_key": {
        "default": "Ctrl+4"
      }
    },
    "fifth_tab": {
      "suggested_key": {
        "default": "Ctrl+5"
      }
    },
    "sixth_tab": {
      "suggested_key": {
        "default": "Ctrl+6"
      }
    },
    "seventh_tab": {
      "suggested_key": {
        "default": "Ctrl+7"
      }
    },
    "eighth_tab": {
      "suggested_key": {
        "default": "Ctrl+8"
      }
    },
    "ninth_tab": {
      "suggested_key": {
        "default": "Ctrl+9"
      }
    },
    "tenth_tab": {
      "suggested_key": {
        "default": "Ctrl+0"
      }
    },
    "pinned_first_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+1"
      }
    },
    "pinned_second_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+2"
      }
    },
    "pinned_third_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+3"
      }
    },
    "pinned_fourth_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+4"
      }
    },
    "pinned_fifth_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+5"
      }
    },
    "pinned_sixth_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+6"
      }
    },
    "pinned_seventh_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+7"
      }
    },
    "pinned_eighth_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+8"
      }
    },
    "pinned_ninth_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+9"
      }
    },
    "pinned_tenth_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+0"
      }
    }
  },
  "background": {
    "scripts": [
      "shortcuts.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": false
    }
  ]
}