Examine source code of Active Tab History

{
  "manifest_version": 2,
  "name": "Active Tab History",
  "version": "0.2.3",
  "description": "Go forward and back active tab history with Alt + Period and Alt + Comma",
  "icons": {
    "48": "icon.svg"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "forward": {
      "description": "Go forward",
      "suggested_key": {
        "default": "Alt+Period"
      }
    },
    "back": {
      "description": "Go back",
      "suggested_key": {
        "default": "Alt+Comma"
      }
    }
  }
}