v0.0.3.pre

• Adds get API.
• Adds namespace indices and APIs indices.create, indices.delete. Namespace support is implemented similar to how the Elasticsearch stack client implements it. But instead of creating a file with a #{Namespace}Client class per namespace, I am dynamically generating them in runtime and including the namespaced methods. These are defined in ElasticsearchServerless::API::#{module_name}::Actions with metaprogramming. This works similar to the old client, but there's less manual work and by adding a namespace to API_NAMESPACES, it's automatically generated. Commit: f97b2a47565f70a1278feba13fd625cbe2cb3134
• Two new sections added to the getting started page: Getting a document and Deleting an index.