feat: add inital in memory dispatcher

Add a simple in memory dispatcher for scalar requests and stream request.

README.md

@@ -0,0 +1,72 @@
+# `Geekeey.Request`
+
+Simple mediator implementation in .NET with minimal dependencies.
+
+## Features
+
+- **Simple interfaces:** no complex constraints, just marker interfaces that work.
+- **Minmal dependencies:** only depends on `Microsoft.Extensions.DependencyInjection.Abstractions` and the
+  `Microsoft.Extensions.Options` package.
+
+## Getting Started
+
+### Install the NuGet package:
+
+```shell
+dotnet add package Geekeey.Request
+```
+
+You may need to add our NuGet feed to your `nuget.config` this can be done by running the following command:
+
+```shell
+dotnet nuget add source -n geekeey https://code.geekeey.de/api/packages/geekeey/nuget/index.json
+```
+
+### Usage
+
+```csharp
+public static Task<int> Main()
+{
+  var collection = new ServiceCollection();
+  collection.AddRequestDispatcher(builder => builder
+      .Add(typeof(ScalarHandler))
+      .Add(typeof(ScalarBehavior)));
+  await using var provider = collection.BuildServiceProvider();
+  var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+  var request = new ScalarRequest { Value = "Hello" };
+  var result = await dispatcher.DispatchAsync(request);
+
+  Console.WriteLine(result);
+  return 0;
+}
+
+public class ScalarRequest : IScalarRequest<string>
+{
+  public string Value { get; set; } = string.Empty;
+}
+
+public class ScalarHandler : IScalarRequestHandler<ScalarTestRequest, string>
+{
+  public Task<string> HandleAsync(ScalarTestRequest request, CancellationToken cancellationToken)
+  {
+    return Task.FromResult($"{request.Value} World");
+  }
+}
+
+public class ScalarBehavior : IScalarRequestBehavior<ScalarTestRequest, string>
+{
+  public async Task<string> HandleAsync(ScalarTestRequest request, ScalarHandlerDelegate<string> next, CancellationToken cancellationToken)
+  {
+    Console.WriteLine("Before");
+    var result = await next(request, cancellationToken);
+    Console.WriteLine("After");
+    return result;
+  }
+}
+```
+
+## Behaviour of the Handlers
+
+Handlers are resolved from either the DI conatiner or are created on the fly but can receive arguments from the DI
+container when being constructed. The same also applied for the request pipeline behaviours.