Add IceRPC to the list of third-party RPC implementations (#15072)

This PR adds IceRPC for C# to the list of RPC implementations in third_party.doc.

IceRPC provides full support for Protobuf. See https://docs.icerpc.dev/protobuf for details.

Closes #15072

COPYBARA_INTEGRATE_REVIEW=https://github.com/protocolbuffers/protobuf/pull/15072 from bernardnormier:add-icerpc 857e34e8ce
PiperOrigin-RevId: 604459237

docs/third_party.md

@@ -132,7 +132,8 @@ These are projects we know about implementing Protocol Buffers for other program
 
 GRPC (http://www.grpc.io/) is Google's RPC implementation for Protocol Buffers. There are other third-party RPC implementations as well.  Some of these actually work with Protocol Buffers service definitions (defined using the `service` keyword in `.proto` files) while others just use Protocol Buffers message objects.
 
-* https://github.com/grpc/grpc (C++, Node.js, Python, Ruby, Objective-C, PHP, C#, Google-official implementation)
+*   https://github.com/grpc/grpc (C++, Node.js, Python, Ruby, Objective-C, PHP,
+    C#, Google-official implementation)
 *   https://zeroc.com/products/ice (Multiple languages)
 *   https://github.com/protobuf-net/protobuf-net (C#/.NET/WCF/VB)
 *   http://www.deltavsoft.com/doc/_external_serialization.html#Protobufs (C++)
@@ -147,9 +148,11 @@ GRPC (http://www.grpc.io/) is Google's RPC implementation for Protocol Buffers.
 *   https://github.com/awakesecurity/gRPC-haskell (Haskell)
 *   https://github.com/Yeolar/raster (C++)
 *   https://github.com/jnordberg/wsrpc (JavaScript Node.js/Browser)
-* https://github.com/pbkit/npm-packages/blob/main/frpc-test/src/index.spec.ts (TypeScript Node.js/Browser)
+*   https://github.com/pbkit/npm-packages/blob/main/frpc-test/src/index.spec.ts
+    (TypeScript Node.js/Browser)
 *   https://github.com/ppissias/xsrpcj (Java)
 *   https://github.com/twitchtv/twirp (Multiple languages)
+*   https://github.com/icerpc/icerpc-csharp (C#)
 
 Inactive: