Create an extension.yml file to provide the plugin description

[owaiskazi19]

Is your feature request related to a problem? Please describe.
Similar to https://github.com/opensearch-project/OpenSearch/blob/2.0/buildSrc/src/main/resources/plugin-descriptor.properties. Create a yml file to send it as a part of request to OpenSearch from SDK.

Describe the solution you'd like
A clear and concise description of what you want to happen.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[minalsha]

Closing in lieu of #3084