docs: Add PyPI version badge to README

- Included a badge displaying the current PyPI version of the SDK.
- Enhances visibility of the latest release for developers.

Assisted-by: Codex

Author: datalogics-kam

README.md

@@ -1,6 +1,7 @@
 # pdfRest Python SDK
 
 [![Tests](https://img.shields.io/github/actions/workflow/status/pdfrest/pdfrest-python/test-and-publish.yml?branch=main&label=tests)](https://github.com/pdfrest/pdfrest-python/actions/workflows/test-and-publish.yml)
+[![PyPI Version](https://img.shields.io/pypi/v/pdfrest)](https://pypi.org/project/pdfrest/)
 [![Python Versions](https://img.shields.io/pypi/pyversions/pdfrest)](https://pypi.org/project/pdfrest/)
 [![llms.txt](https://img.shields.io/badge/llms.txt-available-2ea44f)](https://python.pdfrest.com/llms.txt)