Add to readme re options

protoc-gen-go-restate/README.md

@@ -3,9 +3,12 @@
 This tool generates Go language bindings of `service`s in protobuf definition
 files for Restate.
 
+An example of their use can be found in [examples/codegen](../examples/codegen)
+
 ## Usage
 Via protoc:
 ```shell
+go install github.com/restatedev/sdk-go/protoc-gen-go-restate@latest
 protoc --go_out=. --go_opt=paths=source_relative \
 --go-restate_out=. --go-restate_opt=paths=source_relative service.proto
 ```
@@ -23,10 +26,28 @@ plugins:
       - --pull=always
       - -i
       - ghcr.io/restatedev/protoc-gen-go-restate:latest
+    # alternatively if you prefer to install the binary:
+    # local: protoc-gen-go-restate
     out: .
     opt: paths=source_relative
 ```
 
+# Providing options
+This protoc plugin supports the service and method extensions defined in
+[proto/dev/restate/sdk/go.proto](../proto/dev/restate/sdk/go.proto).
+You will need to use these extensions to define virtual objects in proto.
+
+You can import the extensions with the statement `import "dev/restate/sdk/go.proto";`. Protoc will expect an equivalent directory
+structure containing the go.proto file either locally, or under any of the
+paths provided with `--proto_path`. It may be easier to use
+[buf](https://buf.build/docs/bsr/module/dependency-management) to import:
+```yaml
+# buf.yaml
+version: v2
+deps:
+  - buf.build/restatedev/sdk-go
+```
+
 # Building a docker image
 ```
 KO_DOCKER_REPO=ghcr.io/restatedev ko build --platform=all -B