dnscontrol: Use keys.openpgpkey.org for WKD as a service

keys.openpgp.org can act as a WKD server, with a CNAME record for
the subdomain ‘openpgpkey’ to their server.

See https://keys.openpgp.org/about/usage#wkd-as-a-service.

This helps us in getting/advertising our public key.

λ: curl 'https://wkd.keys.openpgp.org/status/?domain=openpgpkey.sanchayanmaity.net'
CNAME lookup ok: openpgpkey.sanchayanmaity.net resolves to wkd.keys.openpgp.org

λ: gpg --locate-keys --auto-key-locate clear,nodefault,wkd sanchayanmaity.net

dnscontrol/dnsconfig.js

@@ -20,6 +20,7 @@ D('sanchayanmaity.net', REG_NONE, DnsProvider(DNS_DESEC),
     CAA("@", "issue", "letsencrypt.org"),
     CNAME("git" , "sanchayanmaity.net."),
     CNAME("www" , "sanchayanmaity.net."),
+    CNAME("openpgpkey", "wkd.keys.openpgp.org."),
     MX("@", 10, "in1-smtp.messagingengine.com."),
     MX("@", 20, "in2-smtp.messagingengine.com."),
     TXT('@', 'v=spf1 include:spf.messagingengine.com ?all'),