Add DNS Seeder config file for more decentralization

Possibly add an external conf file , like "dnsseeder.conf" to allow the people to add
their own , or other public dns seeders.
It would be an enhancemend and also an nice feature to get more decentralized
And if the current DNS seeders, i know they run through cloudflare , have problems like cloudflare error
then the network still could get DNS records from comunity hosted seeders
