Update SUMMARY.md

Author: nikol-ruseva

SUMMARY.md

@@ -1,5 +1,8 @@
 * [Book "Programming Basics" with Java](README.md)
 * [Preface](chapter-00-preface.md)
+* * [About SoftUni and SoftUni Judge](Content/Preface/about-softuni/about-softuni.md)
+  * [How to Become a Software Developer?](Content/Preface/how-to-become-a-programmer/how-to-become-a-programmer.md)
+  * [More About the Book](Content/Preface/about-the-book/about-the-book.md)
 * [1. First Steps in Programming](chapter-01-first-steps-in-programming.md)
 * [2.1. Simple Calculations](chapter-02-simple-calculations.md)
 * [2.2. Simple Calculations – Exam Problems](chapter-02-simple-calculations-exam-problems.md)