Add example for HTTP/REST API-based `DatasetResolver`

[fkapsahili]

Is your feature request related to a problem? Please describe.

The documentation mentions that DatasetResolver can support remote sources, but currently there's no example showcasing how to implement such an HTTP-based resolver. It would be valuable to demonstrate how to load datasets from HTTP-based services, such as a REST API or remote URLs.

Describe the solution you'd like

Add an example HttpDatasetResolver to the dokimos-example module that showcases:

• Support of URIs like http:// or https://
• Fetching JSON/CSV datasets from remotes
• Basic error handling in cases of network issues
• This could probably use Java's built-in HttpClient for simplicity

The example could look like something like this:

Dataset dataset = registry.resolve("https://api.some-domain.com/qa-dataset-v1.json");

[fkapsahili]

Still relevant. We added ServerDatasetResolver since, but it only handles the dataset:// scheme, so a generic http(s):// example is still worth having. ServerDatasetResolver is a good reference for the HttpClient and error handling.