Babylon.js v5.0 beta phase

Hey team!

You may have noticed that we’ve just entered the beta phase for Babylon.js v5.0. This means that for now on until the release we are working on perf and stability issues only (1 exception: finishing GUI editor)

So we will not take any new feature in (unless good reasons of course) until the release (due in April) so everyone can focus on making 5.0 the best possible release

Thanks all!