[PROPOSAL] Add a link back to source code

[dblock]

What are you proposing?

Add a link to this repo from https://playground.opensearch.org/.

How did you come up with this proposal?

When I went to https://playground.opensearch.org/ the first time I wanted to know what powers it.

What is the user experience going to be?

A link from the homepage on https://playground.opensearch.org/ that takes me back here.

Why should it be built? Any reason not to?

I want to see how you built the playground!

What will it take to execute?

Not sure.

What are remaining open questions?

What should the link say? "Fork me on GitHub"? Something else?

[Flyingliuhub]

Thanks @dblock for the suggestions, I will work on it.