public Builder addDnsServer(@NonNull String address) {
            mConfig.dnsServers.add(address);
            return this;
        }
Add a DNS server to the VPN connection. Both IPv4 and IPv6 addresses are supported.
If none is set, the DNS servers of the default network will be used.

Adding a server implicitly allows traffic from that address family (i.e., IPv4 or IPv6)
to be routed over the VPN.

@param address IPv4 or IPv6 address.
@return this {@link Builder} object to facilitate chaining method calls.
netbare-core/src/main/java/com/github/megatronking/netbare/NetBareConfig.java