Added badges for CI in README (opensearch-project#125)

* Added badges for CI in README

Signed-off-by: Owais Kazi <owaiskazi19@gmail.com>

* Update readme

Signed-off-by: Owais Kazi <owaiskazi19@gmail.com>

* PR comments

Signed-off-by: Owais Kazi <owaiskazi19@gmail.com>

Signed-off-by: Owais Kazi <owaiskazi19@gmail.com>

README.md

@@ -1,8 +1,13 @@
 [![codecov](https://codecov.io/gh/opensearch-project/opensearch-sdk-java/branch/main/graph/badge.svg)](https://codecov.io/gh/opensearch-project/opensearch-sdk-java)
+[![GHA gradle check](https://github.com/opensearch-project/opensearch-sdk-java/actions/workflows/build.yml/badge.svg)](https://github.com/opensearch-project/opensearch-sdk-java/actions/workflows/build.yml)
+[![GHA validate pull request](https://github.com/opensearch-project/opensearch-sdk-java/actions/workflows/wrapper.yml/badge.svg)](https://github.com/opensearch-project/opensearch-sdk-java/actions/workflows/wrapper.yml)
 
-# OpenSearch SDK
+# OpenSearch SDK for Java
 - [Introduction](#introduction)
 - [Contributing](#contributing)
+- [Developer Guide](#developer-guide)
+- [Design](#design)
+- [Maintainers](#maintainers)
 - [Code of Conduct](#code-of-conduct)
 
 ## Introduction
@@ -11,7 +16,15 @@ Opensearch plugins have allowed the extension and ehancements of various core fe
 Read more about extensibility [here](https://github.com/opensearch-project/OpenSearch/issues/1422)
 
 ## Contributing
+See [CONTRIBUTING](CONTRIBUTING.md)
+
+## Developer Guide
 See [DEVELOPER_GUIDE](DEVELOPER_GUIDE.md)
+## Design
+See [DESIGN](DESIGN.md)
+
+## Maintainers
+See [MAINTAINERS](MAINTAINERS.md)
 
 ## Code of Conduct