Revert "Do not include `grpc-reactor` example on Windows"
Revert "Do not include `grpc-reactor` example on Windows"

This reverts commit a2ebe29bb098185046d7741e603ee96d04b0c55b.

Unlike the official `README.md` says, it seems like `reactor-grpc` supports Gradle on Windows:

- https://github.com/salesforce/reactive-grpc/issues/186

line/armeria,line/armeria,anuraaga/armeria,kojilin/armeria,kojilin/armeria,minwoox/armeria,kojilin/armeria,minwoox/armeria,kojilin/armeria,line/armeria,line/armeria,line/armeria,anuraaga/armeria,line/armeria,anuraaga/armeria,minwoox/armeria,minwoox/armeria,kojilin/armeria,minwoox/armeria,anuraaga/armeria,trustin/armeria,trustin/armeria,trustin/armeria,minwoox/armeria,trustin/armeria,anuraaga/armeria,trustin/armeria,kojilin/armeria,anuraaga/armeria,trustin/armeria