MergeGroups initial docs

[lawnjelly]

It's been a while since I wrote any docs so I might need some going over to check this is correct. This is new for 3.6.

Also there's a distinct lack of diagrams, but as these are the most time consuming I'm working on the basis some docs (with diagrams to make later) is better than none at all. If anyone is able to help out with diagrams too, that would be great.

[skyace65]

The content itself looks good but there's two issues.

One we switched over to webp images for the docs, you'll need to convert that. I'd recommend using squoosh

Additionally a lot of these lines are way too long and need to be broken up. stuff like this is an issue

[lawnjelly]

Have resaved as webp and used approx 80 char limit per line (could not for the notes and tips as sphinx doesn't seem to like line breaks there as it breaks the formatting).

[Calinou]

Should be good to merge after applying suggestions.

Also, it might be worth adding a paragraph or note about whether mesh merging works with GridMap and how it interacts with it. As I understand it, mesh merging has no effect on GridMap which already uses MultiMesh internally.

[lawnjelly]

As I understand it, mesh merging has no effect on GridMap which already uses MultiMesh internally.

MergeGroup can in fact bake GridMaps (it is one of the parameters). It defaults to off though, as it is more likely to be useful in GLES2 (which doesn't render MultiMeshes efficiently). This is already noted in the class ref, but I've added a short paragraph at the end.

[mhilbrunner]

Thanks, and thanks for the reviews everyone! Merged.