README: Read online CTA, book-card hero, badges (#9)

* README: add Read online call to action ahead of the PDF download

Points at the browsable book on ssudake.com/books/k8s-worksheet.

* README: book card hero, badges, and a star nudge

The branded card links to the read-online book; release, PDF-download,
and license badges sit under the tagline. The card asset doubles as
the repo's social-preview image (upload via Settings > Social preview
- not settable via API).

Author: sanketsudake

.github/book-card.png

@@ -1,8 +1,14 @@
 # k8s-worksheet
 
+[![Kubernetes Internals Worksheet](.github/book-card.png)](https://ssudake.com/books/k8s-worksheet/)
+
 **Kubernetes Internals Worksheet** — a flow-first prep guide for senior, staff, and principal-level interviews on Kubernetes internals.
 
-**[Download the PDF](https://github.com/sanketsudake/k8s-worksheet/releases/latest/download/kubernetes-internals-worksheet.pdf)** · [all releases](https://github.com/sanketsudake/k8s-worksheet/releases)
+[![Latest release](https://img.shields.io/github/v/release/sanketsudake/k8s-worksheet)](https://github.com/sanketsudake/k8s-worksheet/releases/latest)
+[![PDF downloads](https://img.shields.io/github/downloads/sanketsudake/k8s-worksheet/total?label=PDF%20downloads)](https://github.com/sanketsudake/k8s-worksheet/releases)
+[![License](https://img.shields.io/github/license/sanketsudake/k8s-worksheet)](LICENSE)
+
+**[Read online](https://ssudake.com/books/k8s-worksheet/)** · **[Download the PDF](https://github.com/sanketsudake/k8s-worksheet/releases/latest/download/kubernetes-internals-worksheet.pdf)** · [all releases](https://github.com/sanketsudake/k8s-worksheet/releases)
 
 ## Chapters
 
@@ -38,6 +44,8 @@
 - [Appendices](chapters/appendices.md)
 - [The 30 flows](FLOWS.md)
 
+If the worksheet helps your prep, a ⭐ helps others find it — and watching releases gets you new chapters as they land.
+
 ## Contributing
 
 Build instructions, the writing contract, and the diagram size gate are in [CONTRIBUTING.md](CONTRIBUTING.md).