Implement settings file for Ollama agent

[kborowinski]

Important:

I created another PR that utilizes the OllamaSharp library, featuring context, streaming, and settings support. I strongly recommend reviewing and merging #310. However, if you are unable to use third-party libraries for any reason, please consider this PR instead.

PR Summary

This PR implements basic settings file for Ollama agent:

1. The settings file is stored at $HOME\.aish\agent-config\ollama\ollama.config.json
2. Currently only model and endpoint parameters are stored in the config file.
3. Default config file is created when none exists:

{
    // To use Ollama API service:
    // 1. Install Ollama:
    //      winget install Ollama.Ollama
    // 2. Start Ollama API server:
    //      ollama serve
    // 3. Install Ollama model:
    //      ollama pull phi3

    // Declare Ollama model
    "Model": "phi3",
    // Declare Ollama endpoint
    "Endpoint": "http://localhost:11434"
}

PR Context

This PR allows user to specify custom Ollama model and Ollama enpoint location, instead of hardcoded values.
This partially implements #155 (no history and streaming)

@StevenBucher98 : This is quick and dirty, but I needed the settings file ASAP to test the different models without constant agent recompilation. I'm open for suggestions.

[kborowinski]

@StevenBucher98 I have just discovered OllamaSharp nuget package that would simplify the agent code and provide easy streaming service. Would you consider switching to it?

This is how easy is to setup session and start streaming:

var _ollama = new OllamaApiClient("http://localhost:11434");
var _models = await _ollama.ListLocalModelsAsync();
_ollama.SelectedModel = _models.FirstOrDefault().Name;

await foreach (var stream in _ollama.GenerateAsync("How to list files with PowerShell?"))
{
    Console.Write(stream.Response);
}

Edit: I have the PR it the works, with the streaming and context support.

[daxian-dbw]

OllamaSharp uses the MIT license, so it's totally fine to use it for this agent.

I will close this PR to favor the other one.