Add citation information

[adamltyson]

This PR:

• Adds a citation CFF file
• Adds a citation section to the readme
• Adds a DOI badge
• Adds citation sentence to website

I've tried to make this as simple as maintain as possible. The DOI is the "general" one that represents all versions, and will resolve to the latest one. I've also kept version numbers out of it.

In terms of authors, I just used everyone who had contributed to the software, in the order suggested by Zenodo. The final publication may be different to this, but it seemed a good place to start. I suggest we don't try to hyper-optimise this, and just include everyone. The only maintenance needed will be to add new authors to this list as and when needed. Unfortunately this is in three places, but not sure if that's an issue?

I plonked the citation info on the index page of the website. It could go under "community", but I think we want it to be a bit more obvious than that?

Closes #232

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.71%. Comparing base (b27d7a2) to head (0f3eaf1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #240   +/-   ##
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  Coverage   99.71%   99.71%           
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  Files          13       13           
  Lines         702      702           
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  Hits          700      700           
  Misses          2        2           

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[niksirbi]

It all looks good, I made a few changes:

• I validated the cff file via cffinit and discovered that some fields were invalid, or only valid for specific versions. I've rectified these and I've added more info to the .cff file (e.g. keywords, in case it helps with discoverability).
• I've deleted the 2nd "2024" from the citation sentence, because zenodo populated that from the release date field, which according to the cff spec is version-specific, so I've removed it.
• I used the include directive to directly fetch the citation sentence from README, to be included in index.md. So we have to update 2 places instead of 3.
• I noticed that the author list in pyproject.toml included only me and Chang Huan (because I hadn't touched it in ages). I don't know whether it's important to have the same authors there and in the cff, but probably not. I took the liberty of adding @sfmig there, because I'd say she's as much part of the core dev team as we two are.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud