Examine source code of new-addressable-tabs

{
  "manifest_version": 2,
  "name": "new-addressable-tabs",
  "version": "1.0",
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "id": "{9c1e0105-60d2-41bd-ad53-30f96875db09}"
    }
  },
  "description": "Makes tabs addressable by ctrl+[1-9] keystrokes, consistently with chrome behavior",
  "commands": {
    "tab0": {
      "suggested_key": {
        "default": "Ctrl+1",
        "linux": "Ctrl+1"
      },
      "description": "Switch to tab 1"
    },
    "tab1": {
      "suggested_key": {
        "default": "Ctrl+2",
        "linux": "Ctrl+2"
      },
      "description": "Switch to tab 2"
    },
    "tab2": {
      "suggested_key": {
        "default": "Ctrl+3",
        "linux": "Ctrl+3"
      },
      "description": "Switch to tab 3"
    },
    "tab3": {
      "suggested_key": {
        "default": "Ctrl+4",
        "linux": "Ctrl+4"
      },
      "description": "Switch to tab 4"
    },
    "tab4": {
      "suggested_key": {
        "default": "Ctrl+5",
        "linux": "Ctrl+5"
      },
      "description": "Switch to tab 5"
    },
    "tab5": {
      "suggested_key": {
        "default": "Ctrl+6",
        "linux": "Ctrl+6"
      },
      "description": "Switch to tab 6"
    },
    "tab6": {
      "suggested_key": {
        "default": "Ctrl+7",
        "linux": "Ctrl+7"
      },
      "description": "Switch to tab 7"
    },
    "tab7": {
      "suggested_key": {
        "default": "Ctrl+8",
        "linux": "Ctrl+8"
      },
      "description": "Switch to tab 8"
    },
    "lastTab": {
      "suggested_key": {
        "default": "Ctrl+9",
        "linux": "Ctrl+9"
      },
      "description": "Switch to lastTab"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}