Roadmap for adding `runtime` `gpu` attribute and `hints`.

[williamrowell]

Are there any plans to implement the runtime gpu attribute or to add hints? I'm interested in extending miniwdl-slurm to specify slurm partitions and schedule GPUs, but I need to be able to access gpu and provide custom runtime attributes.

I've mocked up the changes to miniwdl-slurm below, before I learned about the plans to move custom runtime attributes to the hints dict.

https://github.com/williamrowell/miniwdl-slurm/commit/29fc361d169a07b672fad4461ffb3842fb6509a3