Port webgpu_compute example to "native" Nodes

[LeviPesin]

Related issue: -

Description

This PR tries to port the example to the "native" Nodes system.

[sunag]

Thanks!!

[LeviPesin]

What I noticed from trying to port the example:

1. I just noticed that const position = temp( vec3() ); assign( position, add( particle, velocity ) ).build( builder ); can be simplified to just const position = temp( add( particle, velocity ) ); position.build();. @sunag Can you please file another PR to simplify that?
2. We need something for controlling the order-of-execution of nodes - I do not really like constantly writing .build( builder )...
3. We need to completely rework the CondNode to allow not only things like vec3 a; if (b) { a = vec3(0); } else { a = vec3(1); }, but to have arbitrary code in the branches.

[sunag]

@LeviPesin I have been thinking about it for days... Calling .build() to assign, is still an interim solution.
I want to add support to create block code on NodeBuilder and keep CondNode with a behavior like a ? b : c and add IfElseNode like:

IF (  someNode, () => {

} );

IF (  someNode, () => {

} ).ELSE_IF ( someNode, () => {

} ).ELSE( () => {

} );

I have two solution in my mind for these issues, but I prefer to test before, and it might take a while to get ready.