Added sample code to readme.md

[harrowmykel]

Description

This change adds a sample code to readme so that developers can easily get started

Issues Resolved

Closes #27 #46

[dblock]

We have been writing https://github.com/opensearch-project/opensearch-php/blob/main/USER_GUIDE.md - is this duplicate? Maybe the README needs to be clearer to look there for sample code? I also think sample code should be runnable, or exercised in CI, and we would point to a working code, ideally.

[harrowmykel]

Yes, please add the link to the readme.md. I didn't see the sample codes.

Also I have more examples in my sample code. You can add them.

[harrowmykel]

I have updated it and added a new commit

[dblock]

@harrowmykel LGTM, please fix DCO with (git commit -s --amend)?

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (main@cf91bd8). Click here to learn what that means.
The diff coverage is n/a.

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[harrowmykel]

Ok. i have done that

[shyim]

@harrowmykel You have to sign all your commits or squash into one