Texture Canvas examples do not work in 5.0

[andreasplesch]

https://doc.babylonjs.com/extensions/textureCanvas links to two Playground examples which do not seem to work in 5.0.0 but do work in 4.2.0 , for me (Chrome, webgl2, linux).

So this may be more of a TextureCanvas extension issue than a documentation issue. But for now the documentation could link to a 4.2.0 playground (if possible) to avoid confusion.

[sebavan]

I ping @Poolminer there as he is the maintainer for the TextureCanvas so lets see if he is available to help :-)

cc @RaananW and @PirateJC for the follow up.

[PirateJC]

Since Texture Canvas is a community supported feature, until it is updated to work with 5.0, I'll add a note in the doc that makes it clear that the feature should be used with 4.2 and below.

[PirateJC]

Addressed in this PR: #663