Bug: Imgui plugin demo fails compilation

[ethindp]

The IMGUI plugin demo fails the compilation on Windows 10, AMD64, VS 2019. The error is:

[ 98%] Building CXX object _deps/imgui-build/CMakeFiles/bsfImgui.dir/Src/BsImguiDemo.cpp.obj
BsImguiDemo.cpp
_deps\imgui-src\Src\BsImgui.h(49): error C2555: 'bs::ct::ImguiRendererExtension::check': overriding virtual function return type differs and is not covariant from 'bs::RendererExtension::check'
Source\Foundation\bsfCore\Renderer\BsRendererExtension.h(114): note: see declaration of 'bs::RendererExtension::check'
_deps\imgui-src\Src\BsImgui.h(51): error C3668: 'bs::ct::ImguiRendererExtension::render': method with override specifier 'override' did not override any base class methods

I have not checked whether this fails compilation on any other platforms.