docs: add a 2-minute hello scaffold to the README

[KeKs0r]

Summary

• Root README now opens with Get started in 2 minutes (after the blurb, badges, and beta note, before Why chkit and the longer API-sync walkthrough): bun create chkit@latest my-app --example hello, migrate, and the users / events query. The old one-line scaffold pointer is folded into that section.
• packages/create-chkit/README.md lists hello as the default example (two small tables, one migration) and clickbench, and the pick-by-name snippet uses --example hello, matching the published 0.2.0-beta.8 manifest.

Test plan

• Read the root README top to bottom and confirm order: intro, Get started in 2 minutes, Why chkit, From a schema to a working sync.
• Confirm the create-chkit Examples table names hello as default and still documents clickbench.