render graph for highly configurable render pipelines

[mreinstein]

currently the render pipeline for my work-in-progress game is baked into Cobalt.draw :

Cobalt.draw = function (....) {
    all tile, sprite layers

    bloom

    misc. shader effects (old film grain, etc.)

    overlay passes (sprite passes part of ui)

    submit webgpu command encoder
}

For this library to be useful, these rendering steps should be configurable at run time.

[mreinstein]

resolved via #6