Add deprecation warning

Author: yurishkuro

README.md

@@ -1,10 +1,15 @@
+# 🛑🛑🛑 Deprecation Notice 🛑🛑🛑
+
+This repository is scheduled to be deprecated. Please see https://github.com/jaegertracing/jaeger-client-cpp/issues/292.
+
+<hr/>
+
 [![Build Status][ci-img]][ci] [![Coverage Status][cov-img]][cov] [![Appveyor Build][appveyor]][appveyor] [![OpenTracing 1.0 Enabled][ot-img]][ot-url]
 
 ![Ubuntu](https://github.com/jaegertracing/jaeger-client-cpp/workflows/Ubuntu/badge.svg)
 ![MacOS](https://github.com/jaegertracing/jaeger-client-cpp/workflows/MacOS/badge.svg)
 ![Windows](https://github.com/jaegertracing/jaeger-client-cpp/workflows/Windows/badge.svg)
 
-
 # jaeger-client-cpp
 [Jaeger](https://www.jaegertracing.io/) SDK with [OpenTracing API for C++](https://github.com/opentracing/opentracing-cpp) binding.