Add pixi as an environment manager option

[cnrrobertson]

I have been migrating all of my data science work from conda to pixi over the six months. It has benefits in speed and robustness for resolving and installing dependencies from either conda-forge or pip and makes use of a much more deterministic, cross platform, and clean manifest (like poetry). Would there be any interest in adding this as a choice for environment manager?

One note is that pixi has its own dependency file format pixi.toml but can also make use of pyproject.toml files as a manifest (see here) which could build on the current template structure.

If there is interest, I can put together a PR.

[jamesmyatt]

I've been using pixi lately and it's been great.