docs: add description for 'port' validator (#1435)

Author: nodivbyzero

README.md

@@ -106,8 +106,9 @@ validate := validator.New(validator.WithRequiredStructEnabled())
 | datauri | Data URL |
 | fqdn | Full Qualified Domain Name (FQDN) |
 | hostname | Hostname RFC 952 |
-| hostname_port | HostPort |
 | hostname_rfc1123 | Hostname RFC 1123 |
+| hostname_port | HostPort |
+| port | Port number |
 | ip | Internet Protocol Address IP |
 | ip4_addr | Internet Protocol Address IPv4 |
 | ip6_addr | Internet Protocol Address IPv6 |

doc.go

@@ -1331,6 +1331,12 @@ can be used to validate fields typically passed to sockets and connections.
 
 	Usage: hostname_port
 
+# Port
+
+This validates that the value falls within the valid port number range of 1 to 65,535.
+
+	Usage: port
+
 # Datetime
 
 This validates that a string value is a valid datetime based on the supplied datetime format.