updated 'DNS' chapter

- signed-off-by: trimstray <trimstray@gmail.com>

README.md

@@ -368,8 +368,10 @@ Only main chapters:
 
 <p>
 &nbsp;&nbsp;:small_orange_diamond: <a href="http://viewdns.info/"><b>ViewDNS</b></a> - one source for free DNS related tools and information.<br>
+&nbsp;&nbsp;:small_orange_diamond: <a href="https://dnslookup.org/"><b>DNSLookup</b></a> - is an advanced DNS lookup tool.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://dnslytics.com/"><b>DNSlytics</b></a> - online investigation tool.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://dnsspy.io/"><b>DNS Spy</b></a> - monitor, validate and verify your DNS configurations.<br>
+&nbsp;&nbsp;:small_orange_diamond: <a href="https://zonemaster.iis.se/en/"><b>Zonemaster</b></a> - helps you to control how your DNS works.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://findsubdomains.com/"><b>Find subdomains online</b></a> - find subdomains for security assessment penetration test.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://dnsdumpster.com/"><b>DNSdumpster</b></a> - dns recon & research, find & lookup dns records.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://dnstable.com/"><b>DNS Table online</b></a> - search for DNS records by domain, IP, CIDR, ISP.<br>