Examine source code of Env Border

{
  "manifest_version": 2,
  "name": "Env Border",
  "version": "1.0.0",
  "description": "Add a colored border to your site's different environments",
  "permissions": [
    "activeTab",
    "storage",
    "<all_urls>"
  ],
  "icons": {
    "16": "images/env-border-icon-16.png",
    "48": "images/env-border-icon-48.png",
    "128": "images/env-border-icon-128.png"
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "id": "{6ae8035e-7476-45d0-b054-f8ae36331b91}"
    }
  }
}