[Feature Request] Add JSON Tree View for gRPC Responses

Inspecting large and deeply nested JSON responses in the current plain-text format is challenging. It would greatly improve the user experience if grpcui could render gRPC responses in a collapsible JSON tree view, similar to tools like [jsoneditoronline.org](https://jsoneditoronline.org/).

This would help users:

- Easily navigate and explore large JSON responses.
- Quickly identify key fields and values without scrolling through raw text.
- Potentially enable JSONPath-style querying in the future for advanced filtering and validation.

Suggested Implementation Ideas:

- Add a toggle to switch between raw JSON and tree view.
- Use an existing lightweight JSON tree viewer (e.g., [jsoneditor](https://github.com/josdejong/jsoneditor) or similar).
- Optionally allow searching or filtering within the JSON tree.

This feature would make grpcui more user-friendly for developers debugging complex gRPC services. Please let me know your thoughts on this.

The issue names no files, tests, or entry points; begin by locating grpcui's current raw JSON response rendering and the response control where a view toggle could fit. Done means large gRPC JSON responses can switch between raw and collapsible tree views, with any search or filtering limited to the agreed scope.

Written by the indexing model from the issue text.