Examine source code of Rempl

{
  "name": "Rempl",
  "version": "1.0.4",
  "description": "Rempl host for browser's Developer Tools",
  "manifest_version": 2,
  "icons": {
    "16": "img/icon16x16.png",
    "32": "img/icon32x32.png",
    "48": "img/icon48x48.png",
    "128": "img/icon128x128.png"
  },
  "devtools_page": "index.html",
  "sandbox": {
    "pages": [
      "sandbox.html"
    ]
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "page.js"
      ]
    }
  ],
  "applications": {
    "gecko": {
      "id": "rempl@exdis.me",
      "strict_min_version": "57.0"
    }
  }
}