[SamsonPG]

Adds three free, browser-based tool sites to data/Design_and_UI.md (alphabetical, no trailing slash, per CONTRIBUTING):

• TryCalculatingNow: GPA, final-grade, percentage, loan/EMI and income-tax calculators
• TryDevSnip: developer utilities (JSON formatter, cron helper, timestamp converter, JWT decoder, hash generator)
• TryQuickImg: image tools (HEIC to JPG, compress to a KB target, resize, crop, passport and exam photo sizes)

All three are free with no account and no paywall, and they run in the browser. Inputs and images are processed on the user's device.

Disclosure: I'm the maker (Samson PG / Acsaven). Happy to move them to a different category or trim the descriptions if you prefer.