Add rest and grpc example (#967)

* Add rest and grpc example

* remove needless dependencies

* Apply suggestions from code review

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/main.rs

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/main.rs

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/multiplex_service.rs

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/Cargo.toml

Co-authored-by: David Pedersen <[email protected]>

* Update examples/rest-grpc-multiplex/src/multiplex_service.rs

Co-authored-by: David Pedersen <[email protected]>

* clean noisy code

* fix nitpicks

* missing newline

Co-authored-by: David Pedersen <[email protected]>

examples/rest-grpc-multiplex/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    tonic_build::compile_protos("proto/helloworld.proto").unwrap();
+}