Add codecov badge to readme.md file, issue #102

Author: athrane

README.md

@@ -1,4 +1,6 @@
 # Emeritus-agent
+[![codecov](https://codecov.io/gh/<OWNER>/emeritus-agent/branch/main/graph/badge.svg)](https://codecov.io/gh/<OWNER>/emeritus-agent)
+
 Experiment with a belief–desire–intention (BDI) agent for an old man living in a house.
 
 ## Usage