fix: Add cache-busting to PyPI badge

Author: tclark-ufl

README.md

@@ -1,6 +1,6 @@
 # DII Calculator
 
-[![PyPI version](https://img.shields.io/pypi/v/dii-calculator.svg)](https://pypi.org/project/dii-calculator/)
+[![PyPI version](https://img.shields.io/pypi/v/dii-calculator.svg?cacheSeconds=60)](https://pypi.org/project/dii-calculator/)
 [![Python 3.10+](https://img.shields.io/badge/python-3.10+-blue.svg)](https://www.python.org/downloads/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)