Add Nutilz Cron Builder to Generators

[Buddy69-Lanka]

Adds Nutilz Cron Builder to the Generators section.

What it does: a visual, point-and-click cron expression builder — pick minute/hour/day/month/weekday values (or start from a preset like @daily / @weekly / every 15 min), get the generated cron syntax plus a plain-English description of the schedule, and preview the next 10 run times. Also validates hand-written cron expressions.

Meets the contribution notes: browser-based (all parsing/validation runs client-side, no server round-trip), direct link straight to the tool, 100% free with no signup/paywall/usage limits.

[github-actions]

Hey Buddy69-Lanka! 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

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