Fix Metal rendering.

NuGet.Config

@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<configuration>
-  <packageSources>
-    <add key="dotnet-myget dotnet-core" value="https://dotnet.myget.org/F/dotnet-core/api/v3/index.json" />
-  </packageSources>
-</configuration>

src/ImGui.NET.SampleProgram/ImGuiController.cs

@@ -99,8 +99,8 @@ namespace ImGuiNET
 
             byte[] vertexShaderBytes = LoadEmbeddedShaderCode(gd.ResourceFactory, "imgui-vertex", ShaderStages.Vertex);
             byte[] fragmentShaderBytes = LoadEmbeddedShaderCode(gd.ResourceFactory, "imgui-frag", ShaderStages.Fragment);
-            _vertexShader = factory.CreateShader(new ShaderDescription(ShaderStages.Vertex, vertexShaderBytes, "main"));
-            _fragmentShader = factory.CreateShader(new ShaderDescription(ShaderStages.Fragment, fragmentShaderBytes, "main"));
+            _vertexShader = factory.CreateShader(new ShaderDescription(ShaderStages.Vertex, vertexShaderBytes, gd.BackendType == GraphicsBackend.Metal ? "VS" : "main"));
+            _fragmentShader = factory.CreateShader(new ShaderDescription(ShaderStages.Fragment, fragmentShaderBytes, gd.BackendType == GraphicsBackend.Metal ? "FS" : "main"));
 
             VertexLayoutDescription[] vertexLayouts = new VertexLayoutDescription[]
             {
@@ -123,7 +123,8 @@ namespace ImGuiNET
                 PrimitiveTopology.TriangleList,
                 new ShaderSetDescription(vertexLayouts, new[] { _vertexShader, _fragmentShader }),
                 new ResourceLayout[] { _layout, _textureLayout },
-                outputDescription);
+                outputDescription,
+                ResourceBindingModel.Default);
             _pipeline = factory.CreateGraphicsPipeline(ref pd);
 
             _mainResourceSet = factory.CreateResourceSet(new ResourceSetDescription(_layout,