feat: Add zero draft of coffea material

[matthewfeickert]

• Add a zero version draft of the files so that there are placeholder files while others add their materials.
• Add pixi environment files.
• Add jupytext config file.

* Add a zero version draft of the files so that there are placeholder files
  while others add their materials.
* Add pixi environment files.
* Add jupytext config file.

Co-authored-by: Nick Manganelli <nicholas.james.manganelli@cern.ch>
Co-authored-by: Vangelis Kourlitis <evangelos.kourlitis@cern.ch>

[matthewfeickert]

To be clear to anyone else looking at this before the training event, this is just to get some files in. I still need to write most of everything.