Update ImGui.NET to 1.87.3 (dotnet#972)

Author: Beyley

src/OpenGL/Extensions/Silk.NET.OpenGL.Extensions.ImGui/Silk.NET.OpenGL.Extensions.ImGui.csproj

@@ -19,7 +19,7 @@
         <ProjectReference Include="..\..\..\Input\Silk.NET.Input.Common\Silk.NET.Input.Common.csproj" />
         <ProjectReference Include="..\..\Silk.NET.OpenGL\Silk.NET.OpenGL.csproj" />
         <ProjectReference Include="..\..\..\Windowing\Silk.NET.Windowing.Common\Silk.NET.Windowing.Common.csproj" />
-        <PackageReference Include="ImGui.NET" Version="1.86.0" />
+        <PackageReference Include="ImGui.NET" Version="1.87.3" />
     </ItemGroup>
 
     <Import Project="..\..\..\..\build\props\common.props" />

src/OpenGL/Extensions/Silk.NET.OpenGL.Legacy.Extensions.ImGui/Silk.NET.OpenGL.Legacy.Extensions.ImGui.csproj

@@ -24,7 +24,7 @@
         <ProjectReference Include="..\..\..\Input\Silk.NET.Input.Common\Silk.NET.Input.Common.csproj" />
         <ProjectReference Include="..\..\Silk.NET.OpenGL.Legacy\Silk.NET.OpenGL.Legacy.csproj" />
         <ProjectReference Include="..\..\..\Windowing\Silk.NET.Windowing.Common\Silk.NET.Windowing.Common.csproj" />
-        <PackageReference Include="ImGui.NET" Version="1.78.0" />
+        <PackageReference Include="ImGui.NET" Version="1.87.3" />
     </ItemGroup>
 
     <Import Project="..\..\..\..\build\props\common.props" />

src/OpenGL/Extensions/Silk.NET.OpenGLES.Extensions.ImGui/Silk.NET.OpenGLES.Extensions.ImGui.csproj

@@ -23,7 +23,7 @@
         <ProjectReference Include="..\..\..\Input\Silk.NET.Input.Common\Silk.NET.Input.Common.csproj" />
         <ProjectReference Include="..\..\Silk.NET.OpenGLES\Silk.NET.OpenGLES.csproj" />
         <ProjectReference Include="..\..\..\Windowing\Silk.NET.Windowing.Common\Silk.NET.Windowing.Common.csproj" />
-        <PackageReference Include="ImGui.NET" Version="1.78.0" />
+        <PackageReference Include="ImGui.NET" Version="1.87.3" />
     </ItemGroup>
 
     <Import Project="..\..\..\..\build\props\common.props" />