C# bindings (#650)

* First workin version of the C# bindings

* Update README.md

Signed-off-by: mvenditto <venditto.matteo@gmail.com>

* Added more docs + fixed prompt callback signature

* build scripts revision

* Added .editorconfig + fixed style issues

---------

Signed-off-by: mvenditto <venditto.matteo@gmail.com>

gpt4all-bindings/csharp/Gpt4All/Bindings/ILLModel.cs

@@ -0,0 +1,31 @@
+namespace Gpt4All.Bindings;
+
+/// <summary>
+/// Represents the interface exposed by the universal wrapper for GPT4All language models built around llmodel C-API.
+/// </summary>
+public interface ILLModel : IDisposable
+{
+    ModelType ModelType { get; }
+
+    ulong GetStateSizeBytes();
+
+    int GetThreadCount();
+
+    void SetThreadCount(int threadCount);
+
+    bool IsLoaded();
+
+    bool Load(string modelPath);
+
+    void Prompt(
+        string text,
+        LLModelPromptContext context,
+        Func<ModelPromptEventArgs, bool>? promptCallback = null,
+        Func<ModelResponseEventArgs, bool>? responseCallback = null,
+        Func<ModelRecalculatingEventArgs, bool>? recalculateCallback = null,
+        CancellationToken cancellationToken = default);
+
+    unsafe ulong RestoreStateData(byte* destination);
+
+    unsafe ulong SaveStateData(byte* source);
+}