Examine source code of BackspaceBack

{
  "manifest_version": 2,
  "name": "Backspace to Go Back",
  "version": "1.0",
  "description": "Pressing the Backspace key navigates back in history.",
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e2e03364-d7c7-4cac-8989-4c305b5e4ba9}"
    }
  }
}