[DOC] Document for HTTP/3 transport support (server side, experimental)

[reta]

What do you want to do?

Document for HTTP/3 transport support (server side, experimental)

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Tell us about your request. Provide a summary of the request.
See please opensearch-project/OpenSearch#4451 for the context

Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.
3.5.0

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.