docs: Add the badge for the coverage report to the top of the README.md file.

Author: gkapfham

README.md

@@ -6,6 +6,7 @@
 # 🔦 pytest-brightest
 
 [![Build](https://github.com/AstuteSource/pytest-brightest/actions/workflows/build.yml/badge.svg)](https://github.com/AstuteSource/pytest-brightest/actions/workflows/build.yml)
+[![Coverage](https://img.shields.io/badge/dynamic/json?color=brightgreen&label=coverage&query=%24.totals.percent_covered_display&suffix=%25&url=https%3A//raw.githubusercontent.com/wiki/AstuteSource/pytest-brightest/coverage.json)](https://github.com/AstuteSource/pytest-brightest)
 [![Maintenance](https://img.shields.io/badge/maintained%3F-Yes-blue.svg)](https://github.com/AstuteSource/pytest-brightest/graphs/commit-activity)
 [![License LGPL v3](https://img.shields.io/badge/license-LGPL%20v3-blue.svg)](https://www.gnu.org/licenses/lgpl-3.0)