fix: edit registry and metrics readme (#1384)

metrics/README.md

@@ -1,2 +1,6 @@
 # Metrics
-* [Prometheus](https://github.com/go-kratos/prometheus)
+
+## prometheus
+```
+go get -u github.com/go-kratos/kratos/metrics/prometheus/v2
+```

registry/README.md

@@ -1,6 +1,26 @@
 # Registry
-* [Consul](https://github.com/go-kratos/consul)
-* [Etcd](https://github.com/go-kratos/etcd)
-* [Kube](https://github.com/go-kratos/kube)
-* [Nacos](https://github.com/go-kratos/nacos)
 
+## Consul
+```shell
+go get -u github.com/go-kratos/kratos/registry/consul/v2
+```
+
+## Etcd
+```shell
+go get -u github.com/go-kratos/kratos/registry/etcd/v2
+```
+
+## zookeeper
+```shell
+go get -u github.com/go-kratos/kratos/registry/zookeeper/v2
+```
+
+## Kube
+```shell
+go get -u github.com/go-kratos/kratos/registry/kube/v2
+```
+
+## Nacos
+```shell
+go get -u github.com/go-kratos/kratos/registry/nacos/v2
+```