Support for context in generate endpoint

[jmont-dev]

Context tokens are supplied from the generate endpoint. Allow supplying these as an input to additional generations to allow responses that span multiple generations.

[JG-Adams]

I figured out how to do in manual way.
First capture the context.
inline nlohmann::json Keepcontext;
if (response.as_json()["done"]==true) {
prompt_AI.busy=false;
if (response.as_json().contains("context")){
Keepcontext = response.as_json()["context"];
}
}
Then you put it in request in the next time.

ollama::request request(ollama::message_type::generation);
if (!Keepcontext.empty()){
request["context"] = Keepcontext;
}

[jmont-dev]

This was addressed in #23. You can now include previous responses to provide context when using the generate endpoint. See the sections added to the Readme on handling context and context length: https://github.com/jmont-dev/ollama-hpp?tab=readme-ov-file#handling-context.