DOC: Update PyPI downloads badge in README for improved clarity

Author: acsenrafilho

README.md

@@ -5,7 +5,7 @@
 [![CI_main](https://github.com/LOAMRI/asltk/actions/workflows/ci_main.yaml/badge.svg)](https://github.com/LOAMRI/asltk/actions/workflows/ci_main.yaml)
 [![CI_develop](https://github.com/LOAMRI/asltk/actions/workflows/ci_develop.yaml/badge.svg)](https://github.com/LOAMRI/asltk/actions/workflows/ci_develop.yaml)
 ![Python Versions](https://img.shields.io/badge/python-3.9%20|+-blue)
-![PyPI downloads](https://img.shields.io/pypi/dm/asltk)
+[![PyPI downloads](https://img.shields.io/pypi/dm/asltk?label=PyPI%20downloads)](https://pypi.org/project/asltk/)
 ![Contributors](https://img.shields.io/github/contributors/LOAMRI/asltk)
 [![GitHub issues](https://img.shields.io/github/issues-raw/LOAMRI/asltk.svg?maxAge=2592000)]()
 [![GitHub Sponsor](https://img.shields.io/badge/Sponsor-❤️%20acsenrafilho-orange?logo=github)](https://github.com/sponsors/acsenrafilho)