following up from #4 where (experimental) instance mode support was added, there remain some stuff to do:

• extend the P5Instance object to really contain all fields the real instance allows for (they should be more or less all vars in p5js.nim except the vars that represent constants like TWO_PI)
• make sure all procedures that require it are under globalAndLocal
• extend the instance template to not only include setup and draw. This also requires an addition to the P5Instance class for each addition, as each is stored as a closure in the object. All that is in p5sugar.nim should be added. This could be done with a macro but it is simpler via copy & paste.
• allow varargs untyped to p5Instance to pass computed values from c backend to js backend, see example here https://github.com/HugoGranstrom/PointCloudReconstruction/blob/80d6541a10f8c05289b50f9b142386a62bc970c2/presentation/slides.nim#L131