in_health:add explanation of add_host and add_port

Signed-off-by: Takahiro YAMASHITA <[email protected]>

input/health.md

@@ -13,6 +13,8 @@ The plugin supports the following configuration parameters:
 | Interval\_Sec| Interval in seconds between the service checks. Default value is _1_. |
 | Internal\_Nsec| Specify a nanoseconds interval for service checks, it works in conjuntion with the Interval\_Sec configuration key. Default value is _0_.|
 | Alert        | If enabled, it will only generate messages if the target TCP service is down. By default this option is disabled.|
+| Add_Host     | If enabled, hostname is appended to each records. Default value is _false_. |
+| Add_Port     | If enabled, port number is appended to each records. Default value is _false_. |
 
 ## Getting Started