feat(#67): Add codecov baadge to README.md

.github/workflows/codecov.yaml

@@ -3,7 +3,7 @@ name: codecov
 on:
   push:
     branches:
-      - main
+      - master
 jobs:
   codecov:
     name: Upload coverage reports to Codecov

README.md

@@ -3,8 +3,9 @@
 [![Maven Central](https://img.shields.io/maven-central/v/org.eolang/jeo-maven-plugin.svg)](https://maven-badges.herokuapp.com/maven-central/org.eolang/jeo-maven-plugin)
 [![Javadoc](http://www.javadoc.io/badge/org.eolang/jeo-maven-plugin.svg)](http://www.javadoc.io/doc/org.eolang/jeo-maven-plugin)
 [![License](https://img.shields.io/badge/license-MIT-green.svg)](LICENSE.txt)
-[![Hits-of-Code](https://hitsofcode.com/github/objectionary/jeo-maven-plugin?branch=master&label=Hits-of-Code)](https://hitsofcode.com/github/volodya-lombrozo/jtcop/view?branch=main&label=Hits-of-Code)
+[![Hits-of-Code](https://hitsofcode.com/github/objectionary/jeo-maven-plugin?branch=master&label=Hits-of-Code)](https://hitsofcode.com/github/objectionary/jeo-maven-plugin/view?branch=master&label=Hits-of-Code)
 ![Lines of code](https://sloc.xyz/github/objectionary/jeo-maven-plugin)
+[![codecov](https://codecov.io/gh/objectionary/jeo-maven-plugin/branch/master/graph/badge.svg)](https://codecov.io/gh/objectionary/jeo-maven-plugin)
 
 **jeo** stands for "Java EOlang Optimizations". **jeo-maven-plugin** is a Maven
 plugin dedicated to optimizing Java bytecode. The process involves translating