Replace Issuestats, which is very dead (#1054)

Co-authored-by: glados-verma <akashv@google.com>

README.md

@@ -5,8 +5,8 @@ The open-source hardware testing framework.
 
 [![Build Status](https://github.com/google/openhtf/actions/workflows/build_and_deploy.yml/badge.svg?branch=master)](https://github.com/google/openhtf/actions?branch=master)
 [![Coverage Status](https://coveralls.io/repos/google/openhtf/badge.svg?branch=master&service=github)](https://coveralls.io/github/google/openhtf?branch=master)
-
-[Issue Stats](http://issuestats.com/github/google/openhtf)
+[![Percentage of issues still open](http://isitmaintained.com/badge/open/google/openhtf.svg)](http://isitmaintained.com/project/google/openhtf "Percentage of issues still open")
+[![Average time to resolve an issue](http://isitmaintained.com/badge/resolution/google/openhtf.svg)](http://isitmaintained.com/project/google/openhtf "Average time to resolve an issue")
 
 ## Overview
 OpenHTF is a Python library that provides a set of convenient abstractions