Consolidate WebASM feature

[Meakk]

WebASM is useful to embed F3D in a web page.
It could be useful for live examples in the documentation, or even be integrated by users in their web project.

We are already compiling libf3d in the CI so we know it's already working.
However, only some basic tests have been done as a proof of concept but there are probably a lot of issues to fix.

Here are a few related subtasks:

• Complete all the missing bindings (see https://github.com/f3d-app/f3d/blob/master/webassembly/F3DEmscriptenBindings.cxx): Complete javascript bindings #1573
• Test all the different rendering styles and options to determine what is working, and what's broken
• Add some CMake logic to embed user files into the javascript library
• Can we open external files located on the server or is it sandboxed?
• Create more examples
• Package it properly for the release
• Fix touch interaction so it works in mobile browser
• Add more features and controls to https://f3d.app/web/
• Update WASM code and CI once https://gitlab.kitware.com/vtk/vtk/-/merge_requests/11178 is merged
• Fix a first render issue: F3D Web first render is incorrectly lit #1506
• Fix an aliasing issue: F3DWeb has some "aliasing" without SSAO #1555
• Add more dependencies: USD (f3d-web does not support loading OpenUSD files #1676), ...

[mwestphal]

Added a few more items

[mwestphal]

I checked a few items.

[Meakk]

Let's just add a banner for 3.0 explaining the feature is experimental

[Meakk]

Let's just add a banner for 3.0 explaining the feature is experimental

done, I'll move this issue to 3.1