feat: add validator for IPv4 bind address / host:port

[rtomadpg]

Fixes Or Enhances

Here is a little PR to say thank you, for providing your framework.

Let's add a validator for IPv4 bind addresses.

Examples of valid input:

• :9000 for port 9000 on any IP address
• 1.2.3.4:7777 for port 7777 on specific IP address

My use case: I need this validator for an application's config including IP based socket listener addresses, like: :9999 or 127.0.0.1:9999

Make sure that you've checked the boxes below before you submit PR:

• Tests exist or have been written that cover this particular change.

@go-playground/validator-maintainers

[coveralls]

coverage: 74.316% (+0.03%) from 74.291%
when pulling e022a95 on rtomadpg:feat-add-ipv4port
into a947377 on go-playground:master.