Add DevScratchpad to Developer Tools

[Saad-web-spec]

Adds DevScratchpad in alphabetical order under Developer Tools.

Summary

DevScratchpad is a zero-data-collection, 100% client-side developer utility suite.

Why it fits

• Security & Privacy: Executes 100% client-side in browser JavaScript/WASM with zero telemetry and zero server transmission for sensitive developer payloads (JWT, hashes, secrets, SQL, JSON).
• Core Utility Suite: Includes 19+ standalone utilities (JSON Formatter/Validator, JWT Decoder, Hash/HMAC Generator, Diff Checker, Cron Visualizer, Regex Tester, cURL to Fetch/Python, etc.).
• No Friction: Free, open-source, and requires no account creation, login, or installation.
• Rules Adherence: Inserted in strict alphabetical order under \Developer Tools\ with a concise, factual description under 100 characters.

I maintain DevScratchpad, so this is a self-submission.