imgui_impl_dx12: Cast to ImTextureID instead of void* to enable redefinition of ImTextureID (#2015, #301)

diff --git a/examples/imgui_impl_dx12.cpp b/examples/imgui_impl_dx12.cpp
index af80c1d..a8b1c70 100644
--- a/examples/imgui_impl_dx12.cpp
+++ b/examples/imgui_impl_dx12.cpp
@@ -365,7 +365,7 @@
 
     // Store our identifier
     static_assert(sizeof(ImTextureID) >= sizeof(g_hFontSrvGpuDescHandle.ptr), "Can't pack descriptor handle into TexID, 32-bit not supported yet.");
-    io.Fonts->TexID = (void *)g_hFontSrvGpuDescHandle.ptr;
+    io.Fonts->TexID = (ImTextureID)g_hFontSrvGpuDescHandle.ptr;
 }
 
 bool    ImGui_ImplDX12_CreateDeviceObjects()