Add WithBody with IDictionary (form-urlencoded values) (#903)

* .

* x

* fx

* fix

* f

* tests

* fix tests

* add tst

src/WireMock.Net/Models/BodyData.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.Text;
 using WireMock.Types;
 
@@ -14,6 +15,9 @@ public class BodyData : IBodyData
     /// <inheritdoc />
     public string? BodyAsString { get; set; }
 
+    /// <inheritdoc />
+    public IDictionary<string, string>? BodyAsFormUrlEncoded { get; set; }
+
     /// <inheritdoc cref="IBodyData.BodyAsJson" />
     public object? BodyAsJson { get; set; }