Introduce the make task to test release without publish

Before the marking the release it is usefull
to test if docker image is working correctly.
Use goreleaser to test how it builds the image
and run tests with commands:

```shell
$ docker run --name toxiproxy-server -d --net=host -it ghcr.io/shopify/toxiproxy:2.1.6-next-amd64
$ docker run --entrypoint=/toxiproxy-cli --rm --net=host -it ghcr.io/shopify/toxiproxy:2.1.6-next-amd64 list
$ docker run --entrypoint=/toxiproxy-cli --rm --net=host -it ghcr.io/shopify/toxiproxy:2.1.6-next-amd64 create -l localhost:3000 -u localhost:80 local
$ docker run --entrypoint=/toxiproxy-cli --rm --net=host -it ghcr.io/shopify/toxiproxy:2.1.6-next-amd64 list
$ docker stop toxiproxy-server
$ docker rm toxiproxy-server
```

Makefile

@@ -33,6 +33,10 @@ build: dist clean
 release:
 	goreleaser release --rm-dist
 
+.PHONY: release-dry
+release-dry:
+	goreleaser release --rm-dist --skip-publish --skip-validate --snapshot
+
 .PHONY: setup
 setup:
 	go mod download