Add TCP rerouting example to main README

Author: SiiiTschiii

README.md

@@ -23,6 +23,7 @@
 - [HTTP Configuration](./examples/http_config/)
 - [gRPC Auth (random)](./examples/grpc_auth_random/)
 - [Envoy filter metadata](./examples/envoy_filter_metadata/)
+- [TCP Rerouting](./examples/tcp_rerouting/)
 
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