updated README.md with contribution section

Author: shekhargulati

README.md

@@ -3,6 +3,10 @@ Java 8: The Missing Tutorial
 
 Java 8 is not a new topic anymore. There are many good books published on it. Still I meet many Java developers unaware of the power of Java 8. The goal of this microbook is to cover some of the most important Java 8 features and how they can help developers in their day to day programming. This is based on my [7 days with Java 8](http://shekhargulati.com/7-days-with-java-8/) blog series.
 
+## Contributing to the Java 8: The Missing Tutorial
+
+Please contribute if you see an error or something that could be better! Raise an [issue](https://github.com/shekhargulati/java8-the-missing-tutorial/issues) or send me a pull request to improve. Contributions of all kinds, including corrections, additions, improvements, and translations, are welcome!
+
 ## Table of Contents
 
 * [Default and Static Methods for Interfaces](./01-default-static-interface-methods.md)