Added challenges section into readme file, with a list of links to codepens for specific challenges. Added codepen link for challenge jonasschmedtmann#2 of section 02.

Author: mirmak4

README.md

@@ -1,3 +1,8 @@
+# Challenges
+
+-   Section 2 code pens:
+    -   Challenge #2: https://codepen.io/mirmak4/pen/vYQZedr?editors=1000
+
 # Course Material and FAQ for "Build Responsive Real-World Websites with HTML and CSS"
 
 This repo contains starter files and final code for all sections and projects contained in the course.