Add JSON Utils (jsonutils.org) to Online tools

[vallme2003]

Hi! I'd like to suggest adding JSON Utils to the Online tools section.

What is it?
JSON Utils is a free, privacy-first collection of 50+ browser-based JSON tools for developers. All processing happens client-side — no data is sent to any server, and no sign-up is required.

Key tools include:

• Core: Formatter, Validator, Minifier, JSON to CSV
• Converters: JSON to Code (C#, Java, TypeScript, Python, Go, Rust, Kotlin, Swift), JSON to SQL, GraphQL, OpenAPI, YAML, XML, Protobuf, Pydantic, Zod, and more
• Analysis: Tree Viewer, JSONPath Parser, Schema Generator/Validator, Diff, Compare, Linter, Size Analyzer
• Utilities: Mock Generator, jq Playground, JWT Decoder, JSON Repair, i18n Manager

Why it fits this list:

• Significantly broader than most existing entries in the Online tools section (50+ tools vs. single-purpose sites)
• Completely free, no registration, privacy-focused (all client-side)
• Covers converters, analysis, and utilities in one place

Suggested entry:

* [JSON Utils](https://jsonutils.org/) - 50+ free, privacy-first online JSON tools including formatter, validator, converters, schema tools, and a jq playground.

Note: There is already an entry for jsonutils.com in the list — that is a different site focused on generating C#/VB.Net/JS classes from JSON. jsonutils.org is a separate, broader toolkit.

Submitted a PR here - #162. Thanks!