Examine source code of Close Tabs Shortcuts Pro

{
  "manifest_version": 2,
  "name": "Close Tabs Shortcuts",
  "version": "1.2.2",
  "description": "Adds keyboard shortcuts for closing all not active tabs, all to the left of the active one, all to the right",
  "background": {
    "scripts": [
      "utils.js",
      "background.js"
    ]
  },
  "commands": {
    "close-other-tabs": {
      "suggested_key": {
        "default": "Alt+W"
      },
      "description": "Close Other Tabs"
    },
    "close-left-tabs": {
      "suggested_key": {
        "default": "Alt+Shift+F1"
      },
      "description": "Close Left Tabs"
    },
    "close-right-tabs": {
      "suggested_key": {
        "default": "Alt+Shift+F2"
      },
      "description": "Close Right Tabs"
    }
  },
  "permissions": [
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ef17f45a-45d8-48e2-a756-c1aacb32980b}"
    }
  }
}