Update README.md with latest info about Verge3D

[alexkowel]

Verge3D supports Maya now. Also add example projects and links to the manual for each product.

[javagl]

^{(Just a short note for someone who merges this PR: It might become obsolete when the README tables are replaced with the project explorer, as discussed in KhronosGroup/glTF-Project-Explorer#37 (comment) - I'm also leaving this comment here as a reminder for myself to update the project explorer data with the information that was added in this PR...)}

[javagl]

The tables in the main glTF README have essentially been replaced by the glTF Project Explorer. I have added the information that you had added to the tables there, via KhronosGroup/glTF-Project-Explorer#44

(I hesitated a bit to add Verge3D 4 times, but since people might just type e.g. "Blender" into the search-by-title bar, and expect to see Blender-related exporters, it's probably reasonable to dedicatedly list the Blender/Max/Maya exporters there).

If there is further information to be added to the Project Explorer, this can also be done via PRs or by opening an issue.

[alexkowel]

Awesome!

(I hesitated a bit to add Verge3D 4 times, but since people might just type e.g. "Blender" into the search-by-title bar, and expect to see Blender-related exporters, it's probably reasonable to dedicatedly list the Blender/Max/Maya exporters there).

Indeed, this greatly improves searching by a modeling suite. Thank you!