Examine source code of Crl-Digit

{
  "name": "Crl-Digit",
  "description": "Use the correct keys on Mac/Linux",
  "manifest_version": 2,
  "version": "1.0.0",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "tab-1": {
      "suggested_key": {
        "default": "Ctrl+1",
        "mac": "MacCtrl+1"
      },
      "description": "Switch to tab #1"
    },
    "tab-2": {
      "suggested_key": {
        "default": "Ctrl+2",
        "mac": "MacCtrl+2"
      },
      "description": "Switch to tab #2"
    },
    "tab-3": {
      "suggested_key": {
        "default": "Ctrl+3",
        "mac": "MacCtrl+3"
      },
      "description": "Switch to tab #3"
    },
    "tab-4": {
      "suggested_key": {
        "default": "Ctrl+4",
        "mac": "MacCtrl+4"
      },
      "description": "Switch to tab #4"
    },
    "tab-5": {
      "suggested_key": {
        "default": "Ctrl+5",
        "mac": "MacCtrl+5"
      },
      "description": "Switch to tab #5"
    },
    "tab-6": {
      "suggested_key": {
        "default": "Ctrl+6",
        "mac": "MacCtrl+6"
      },
      "description": "Switch to tab #6"
    },
    "tab-7": {
      "suggested_key": {
        "default": "Ctrl+7",
        "mac": "MacCtrl+7"
      },
      "description": "Switch to tab #7"
    },
    "tab-8": {
      "suggested_key": {
        "default": "Ctrl+8",
        "mac": "MacCtrl+8"
      },
      "description": "Switch to tab #8"
    },
    "tab-9": {
      "suggested_key": {
        "default": "Ctrl+9",
        "mac": "MacCtrl+9"
      },
      "description": "Switch to tab #9"
    }
  }
}