Support Extended Error Codes in static-responder

[folbricht]

Adds support for extended error codes as per https://datatracker.ietf.org/doc/html/rfc8914 to the static-responder. This can be used to return additional information when a query is blocked. For this the static-responder could be set as the blocklist-resolver for blocklist-v2 for example.

[groups.static]
type  = "static-responder"
edns0-ede = {code = 15, text = "Blocked because reasons"}

Implements #345