coverage badge in README

The CI coverage badge in the README file was not clickable. This commit makes the badge link to the reinforcement-learning project on GitHub, allowing users to easily navigate to the project page.

README.md

@@ -1,4 +1,4 @@
-![Coverage](https://img.shields.io/endpoint?url=https://gist.githubusercontent.com/nakashima-hikaru/39e7ad55fb0943a43d055782915a2024/raw/pytest-coverage-comment.json)
+[![Coverage](https://img.shields.io/endpoint?url=https://gist.githubusercontent.com/nakashima-hikaru/39e7ad55fb0943a43d055782915a2024/raw/pytest-coverage-comment.json)](https://github.com/nakashima-hikaru/reinforcement-learning)
 
 # Reinforcement Learning Project