Gmail HTML Editor

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "name": "Gmail HTML Editor",
  "version": "1.2.0",
  "description": "Edit Gmail emails as HTML.",
  "host_permissions": [
    "https://mail.google.com/"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "assets/edit.png",
        "iframe.html"
      ],
      "matches": [
        "https://mail.google.com/*"
      ]
    }
  ],
  "icons": {
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "run_at": "document_end"
    }
  ],
  "manifest_version": 3
}