Add a resource for DNS (#3096)

* Update 103-dns-and-how-it-works.md

Addition resources added to understand Domain Names

* Update content/roadmaps/101-backend/content/100-internet/103-dns-and-how-it-works.md

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

content/roadmaps/101-backend/content/100-internet/103-dns-and-how-it-works.md

@@ -5,6 +5,7 @@ The Domain Name System (DNS) is the phonebook of the Internet. Humans access inf
 <ResourceGroupTitle>Free Content</ResourceGroupTitle>
 <BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.cloudflare.com/en-gb/learning/dns/what-is-dns/'>What is DNS?</BadgeLink>
 <BadgeLink colorScheme='yellow' badgeText='Read' href='https://howdns.works/'>How DNS works (comic)</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://developer.mozilla.org/en-US/docs/Glossary/DNS/'>Understanding Domain names</BadgeLink>
 <BadgeLink badgeText='Watch' href='https://www.youtube.com/watch?v=Wj0od2ag5sk'>DNS and How does it Work?</BadgeLink>
 <BadgeLink badgeText='Watch' href='https://www.youtube.com/watch?v=7lxgpKh_fRY'>DNS Records</BadgeLink>
 <BadgeLink badgeText='Watch' href='https://www.youtube.com/watch?v=zEmUuNFBgN8&list=PLTk5ZYSbd9MhMmOiPhfRJNW7bhxHo4q-K'>Complete DNS mini-series</BadgeLink>