New configuration feature: specify host rows with IP address.

I have a Vagrant configuration with multiple private networks and I needed host entries for all of them with specific IP addresses. So I added a new configuration feature that allows user to add entries with IP address.

For example:

    Vagrant.configure("2") do |config|
        config.vm.define "example" do |server|
            
            server.hostmanager.alias "hostname.alias", ip: "192.168.0.1"

        end
    end

Decided to share this if anyone else finds it useful. Of course, comments are appreciated.