YAGNI description and resources (#1019)

* YAGNI description and resources

Add description and resources for YAGNI software development/design principle

* Update 105-yagni.md

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

content/roadmaps/101-backend/content/114-design-and-development-principles/105-yagni.md

@@ -1 +1,7 @@
-# Yagni
+# YAGNI
+
+You Aren't Going to Need It (YAGNI) is a software design principle from the Extreme Programming (XP) framework that states when developing software, functionality or features should not be added until they are necessary. Within agile software development in general, requirements are always open to change; any extra functionality may end up being wasted time and resources.
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://martinfowler.com/bliki/Yagni.html'>Yagni</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://deviq.com/principles/yagni'>YAGNI</BadgeLink>