Add JOSS citation information

[andreww]

We should probably add a CITATION.cff file (see text below) and a link to the JOSS paper in the documentation.

Documentation link examples:

Markdown:
[![DOI](https://joss.theoj.org/papers/10.21105/joss.08251/status.svg)](https://doi.org/10.21105/joss.08251)

HTML:
<a style="border-width:0" href="https://doi.org/10.21105/joss.08251">
  <img src="https://joss.theoj.org/papers/10.21105/joss.08251/status.svg" alt="DOI badge" >
</a>

reStructuredText:
.. image:: https://joss.theoj.org/papers/10.21105/joss.08251/status.svg
   :target: https://doi.org/10.21105/joss.08251

cff file:

cff-version: "1.2.0"
authors:
- family-names: Bartholomew
  given-names: Sadie L.
  orcid: "https://orcid.org/0000-0002-6180-3603"
- family-names: Colling
  given-names: Lincoln
  orcid: "https://orcid.org/0000-0002-3572-7758"
- family-names: Dasgupta
  given-names: Abhishek
  orcid: "https://orcid.org/0000-0003-4420-0656"
- family-names: Greenberg
  given-names: Anthony J.
  orcid: "https://orcid.org/0000-0003-3296-5811"
- family-names: Lannelongue
  given-names: Loïc
  orcid: "https://orcid.org/0000-0002-9135-1345"
- family-names: Lestang
  given-names: Thibault
  orcid: "https://orcid.org/0000-0001-6770-2638"
- family-names: Martinez-Ortiz
  given-names: Carlos
  orcid: "https://orcid.org/0000-0001-5565-7577"
- family-names: Sauzé
  given-names: Colin
  orcid: "https://orcid.org/0000-0001-5368-9217"
- family-names: Walker
  given-names: Andrew M.
  orcid: "https://orcid.org/0000-0003-3121-3255"
- family-names: Ward
  given-names: Adam Stuart
  orcid: "https://orcid.org/0009-0008-3463-2694"
contact:
- family-names: Walker
  given-names: Andrew M.
  orcid: "https://orcid.org/0000-0003-3121-3255"
doi: 10.5281/zenodo.15753041
message: If you use this software, please cite our article in the
  Journal of Open Source Software.
preferred-citation:
  authors:
  - family-names: Bartholomew
    given-names: Sadie L.
    orcid: "https://orcid.org/0000-0002-6180-3603"
  - family-names: Colling
    given-names: Lincoln
    orcid: "https://orcid.org/0000-0002-3572-7758"
  - family-names: Dasgupta
    given-names: Abhishek
    orcid: "https://orcid.org/0000-0003-4420-0656"
  - family-names: Greenberg
    given-names: Anthony J.
    orcid: "https://orcid.org/0000-0003-3296-5811"
  - family-names: Lannelongue
    given-names: Loïc
    orcid: "https://orcid.org/0000-0002-9135-1345"
  - family-names: Lestang
    given-names: Thibault
    orcid: "https://orcid.org/0000-0001-6770-2638"
  - family-names: Martinez-Ortiz
    given-names: Carlos
    orcid: "https://orcid.org/0000-0001-5565-7577"
  - family-names: Sauzé
    given-names: Colin
    orcid: "https://orcid.org/0000-0001-5368-9217"
  - family-names: Walker
    given-names: Andrew M.
    orcid: "https://orcid.org/0000-0003-3121-3255"
  - family-names: Ward
    given-names: Adam Stuart
    orcid: "https://orcid.org/0009-0008-3463-2694"
  date-published: 2025-07-08
  doi: 10.21105/joss.08251
  issn: 2475-9066
  issue: 111
  journal: Journal of Open Source Software
  publisher:
    name: Open Journals
  start: 8251
  title: "CATS: The Climate Aware Task Scheduler"
  type: article
  url: "https://joss.theoj.org/papers/10.21105/joss.08251"
  volume: 10
title: "CATS: The Climate Aware Task Scheduler"