Created Visualizer.java

[Nisheshg5]

A class to easily visualize linked list and binary tree in Java. You just need to pass the head node or the root to the static methods.

[hediet]

Hey, thank you for your PR ;) I appreciate the effort you put into it!
What do you think of using a JSON serializer rather than building the string on your own?

Have you had a look at the java demo?

[Nisheshg5]

I did. But I was having issues with the import and I have no experience with JSON, so I decided to use Map and List to manually create a string.
This is easier for beginners like me to understand and thought it may help others too.