Add DevToolkit to Transformation

[ghassan-gaidi]

Adds DevToolkit to the Transformation section.

• Free browser toolkit: JWT decoder, cron expression explainer, Unix epoch ⇄ date, UUID v4 generator, SHA-256/384/512 hashing, JSON formatter/validator, Base64 + URL codecs
• 100% client-side — nothing leaves the device; works offline once loaded
• No signup, no tracking

Placed alphabetically after JSONFormatOnline. Thanks for maintaining the list!

[github-actions]

Hey ghassan-gaidi! Thanks for your submission! 🚀

To keep awesome-devtools instantly accessible for everyone, all tools must be:

• Browser-based — no downloads or native app installs
• Direct link — goes straight to the tool (not a multi-tool landing page)
• 100% free — no signups, trials, paywalls, or usage limits

Please make sure your PR meets these criteria. It may take some time for your submission to be reviewed — you can occasionally comment with a "bump" to bring more attention to it.

Thanks for contributing! 🙌