VImpl: A Virtual Take on the C++ PImpl Pattern

It's probably not super original but maybe some people will appreciate the ergonomics! So basically, classic pimpl is a lot of ceremony to decouple your header from member dependencies. VImpl (virtual impl) is solving the same issue with very similar performance penalties but has almost no boilerplate compared to the original C++ header/source separation. I think that's pretty neat so if it helps some people, that'd be great!