Examine source code of Let me Leave

{
  "manifest_version": 2,
  "name": "Lemme Leave",
  "version": "1.0",
  "description": "Prevent website to change behaviour when leaving. Block the popup when your cursor leaves the page. Prevent pausing video ads when changing focus.",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "page.js"
  ],
  "browser_action": {
    "browser_style": true,
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "128": "icons/icon-128.png"
  }
}