Add badge to Bugzilla

Author: wilzbach

README.md

@@ -2,6 +2,7 @@ DRuntime: Runtime Library for the D Programming Language
 ========================================================
 
 [![GitHub tag](https://img.shields.io/github/tag/dlang/druntime.svg?maxAge=86400)](https://github.com/dlang/druntime/releases)
+[![Bugzilla Issues](https://img.shields.io/badge/issues-Bugzilla-green.svg)](https://issues.dlang.org/buglist.cgi?component=druntime&list_id=220148&product=D&resolution=---)
 [![Build status](https://img.shields.io/circleci/project/dlang/druntime.svg?maxAge=86400)](https://circleci.com/gh/dlang/druntime)
 [![Code coverage](https://img.shields.io/codecov/c/github/dlang/druntime.svg?maxAge=86400)](https://codecov.io/gh/dlang/druntime)
 [![Issue Stats](https://img.shields.io/issuestats/p/github/dlang/druntime.svg?maxAge=2592000)](http://www.issuestats.com/github/dlang/druntime)