Update readme.md

readme.md

@@ -7,3 +7,50 @@
 [![GitHub issues-closed](https://img.shields.io/github/issues-closed/viceroypenguin/Immediate.Apis.svg)](https://GitHub.com/viceroypenguin/Immediate.Apis/issues?q=is%3Aissue+is%3Aclosed) 
 [![GitHub Actions](https://github.com/viceroypenguin/Immediate.Apis/actions/workflows/build.yml/badge.svg)](https://github.com/viceroypenguin/Immediate.Apis/actions)
 ---
+
+Immediate.Apis is a source generator for minimal APIs, for
+[`Immediate.Handlers`](https://github.com/viceroypenguin/Immediate.Handlers) handlers. Simply add a `[MapGet]` to the
+`[Handler]` class and an endpoint will automatically be added.
+
+#### Examples
+* [Immediate.Apis.FunctionalTests](./tests/Immediate.Apis.FunctionalTests)
+
+## Installing Immediate.Apis
+
+You can install [Immediate.Apis with NuGet](https://www.nuget.org/packages/Immediate.Apis):
+
+    Install-Package Immediate.Apis
+
+Or via the .NET Core command line interface:
+
+    dotnet add package Immediate.Apis
+
+Either commands, from Package Manager Console or .NET Core CLI, will download and install Immediate.Handlers.
+
+## Using Immediate.Apis
+### Creating an Endpoint
+
+Create a Handler and an endpoint by adding the following code:
+
+```cs
+[Handler]
+[MapGet("/users")]
+public static partial class GetUsersQuery
+{
+    public record Query;
+
+    private static ValueTask<IEnumerable<User>> HandleAsync(
+        Query _,
+        UsersService usersService,
+        CancellationToken token)
+    {
+        return usersService.GetUsers();
+    }
+}
+```
+
+### Registering the endpoints
+
+In your `Program.cs`, add a call to `app.MapXxxEndpoints()`, where `Xxx` is the shortened form of the project name.
+* For a project named `Web`, it will be `app.MapWebEndpoints()`
+* For a project named `Application.Web`, it will be `app.MapApplicationWebEndpoints()`