Allow running the code in online playground

[jankeromnes]

Hi @joeyajames 👋

I work on gitpod.io, an online development environment for GitHub, and I thought your viewers might be interested in having a way to edit & run your code online, without having to install anything on their computer.

In this Pull Request, I've configured Gitpod to:

• go into the Java 8 Streams directory
• open JavaStreams.java in the Editor
• compile and run this file in the Terminal

You can try this configuration by following this link (using my fork):
https://gitpod.io/#https://github.com/jankeromnes/Java

Here is what it will look like:

Please let me know what you think. 🙂