Add books to Java Roadmap Fundamentals (#1580)

* Add books to Java Roadmap Fundamentals

* Update content/roadmaps/110-java/content/100-java-fundamentals/readme.md

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

content/roadmaps/110-java/content/100-java-fundamentals/readme.md

@@ -1 +1,15 @@
-# Java fundamentals
+# Java Fundamentals
+
+Learn about the fundamentals of Java such as basic syntax, data types, variables, conditionals, functions, data structures, packages, etc. 
+
+<ResourceGroupTitle>Free Resources</ResourceGroupTitle>
+
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.w3schools.com/java/'>Java Basics - W3Schools</BadgeLink>
+
+<ResourceGroupTitle>Books</ResourceGroupTitle>
+
+<BadgeLink colorScheme='purple' badgeText='Book' href='https://www.amazon.co.uk/Head-First-Java-3rd-Brain-Friendly/dp/1491910771>Head First Java</BadgeLink>
+<BadgeLink colorScheme='purple' badgeText='Book' href='https://www.amazon.co.uk/Thinking-Java-Eckel-Bruce-February/dp/B00IBON6C6'>Thinking in Java</BadgeLink>
+<BadgeLink colorScheme='purple' badgeText='Book' href='https://www.amazon.com/Effective-Java-Joshua-Bloch/dp/0134685997'>Effective Java</BadgeLink>
+<BadgeLink colorScheme='purple' badgeText='Book' href='https://www.amazon.co.uk/Java-Beginners-Guide-Herbert-Schildt/dp/1260463559'>Java: A Beginner's Guide</BadgeLink>
+<BadgeLink colorScheme='purple' badgeText='Book' href='https://www.amazon.co.uk/gp/product/B09JL8BMK7/ref=dbs_a_def_rwt_bibl_vppi_i2'>Java: The Complete Reference</BadgeLink>