doc: add IPv6 doc

spring-cloud-alibaba-docs/src/main/asciidoc-zh/nacos-discovery.adoc

@@ -313,6 +313,7 @@ Endpoint 暴露的 json 中包含了两种属性:
 |权重|`spring.cloud.nacos.discovery.weight`|`1`|取值范围 1 到 100，数值越大，权重越大
 |网卡名|`spring.cloud.nacos.discovery.network-interface`||当IP未配置时，注册的IP为此网卡所对应的IP地址，如果此项也未配置，则默认取第一块网卡的地址
 |注册的IP地址|`spring.cloud.nacos.discovery.ip`||优先级最高
+|注册的IP地址类型|`spring.cloud.nacos.discovery.ip-type`|`IPv4`|可以配置IPv4和IPv6两种类型
 |注册的端口|`spring.cloud.nacos.discovery.port`|`-1`|默认情况下不用配置，会自动探测
 |命名空间|`spring.cloud.nacos.discovery.namespace`||常用场景之一是不同环境的注册的区分隔离，例如开发测试环境和生产环境的资源（如配置、服务）隔离等
 |AccessKey|`spring.cloud.nacos.discovery.access-key`||当要上阿里云时，阿里云上面的一个云账号名

spring-cloud-alibaba-docs/src/main/asciidoc/nacos-discovery.adoc

@@ -315,6 +315,7 @@ The following shows the other configurations of the starter of Nacos Discovery:
 |Weight|`spring.cloud.nacos.discovery.weight`|`1`|Value range: 1 to 100. The bigger the value, the greater the weight
 |Network card name|`spring.cloud.nacos.discovery.network-interface`||If the IP address is not specified, the registered IP address is the IP address of the network card. If this is not specified either, the IP address of the first network card will be used by default.
 |Registered IP address|`spring.cloud.nacos.discovery.ip`||Highest priority
+|Registered IP address Type|`spring.cloud.nacos.discovery.ip-type`|`IPv4`|IPv4 and IPv6 can be configured
 |Registered port|`spring.cloud.nacos.discovery.port`|`-1`|Will be detected automatically by default. Do not need to be configured.
 |Namespace|`spring.cloud.nacos.discovery.namespace`||A typical scenario is to isolate the service registration for different environment, such as resource (configurations, services etc.) isolation between testing and production environment
 |AccessKey|`spring.cloud.nacos.discovery.access-key`||Alibaba Cloud account accesskey

spring-cloud-alibaba-examples/nacos-example/nacos-discovery-example/readme-zh.md

@@ -191,6 +191,7 @@ Spring Boot 2.x 可以通过访问 http://127.0.0.1:18083/actuator/nacos-discove
 权重|spring.cloud.nacos.discovery.weight|1|取值范围 1 到 100，数值越大，权重越大
 网卡名|spring.cloud.nacos.discovery.network-interface||当IP未配置时，注册的IP为此网卡所对应的IP地址，如果此项也未配置，则默认取第一块网卡的地址
 注册的IP地址|spring.cloud.nacos.discovery.ip||优先级最高
+注册的IP地址类型|spring.cloud.nacos.discovery.ip-type|IPv4|可以配置IPv4和IPv6两种类型
 注册的端口|spring.cloud.nacos.discovery.port|-1|默认情况下不用配置，会自动探测
 命名空间|spring.cloud.nacos.discovery.namespace||常用场景之一是不同环境的注册的区分隔离，例如开发测试环境和生产环境的资源（如配置、服务）隔离等。
 AccessKey|spring.cloud.nacos.discovery.access-key||

spring-cloud-alibaba-examples/nacos-example/nacos-discovery-example/readme.md

@@ -198,6 +198,7 @@ server address|spring.cloud.nacos.discovery.server-addr||
 service|spring.cloud.nacos.discovery.service|spring.application.name|service id to registry
 weight|spring.cloud.nacos.discovery.weight|1|value from 1 to 100, The larger the value, the larger the weight
 ip|spring.cloud.nacos.discovery.ip||ip address to registry, Highest priority
+ip type|spring.cloud.nacos.discovery.ip-type|IPv4|IPv4 and IPv6 can be configured
 network interface|spring.cloud.nacos.discovery.network-interface||When the IP is not configured, the registered IP address is the IP address corresponding to the network-interface. If this item is not configured, the address of the first network-interface is taken by default.
 port|spring.cloud.nacos.discovery.port|-1|port to registry, Automatically detect without configuration
 namesapce|spring.cloud.nacos.discovery.namespace||One of the common scenarios is the separation of the configuration of different environments, such as the development of the test environment and the resource isolation of the production environment.