Add bibtex metadata retrieval

[znicholls]

Description

Checklist

Please confirm that this pull request has done the following:

• Tests added
• Documentation added (where applicable)
• Changelog item added to changelog/

[codecov]

Codecov Report

Attention: Patch coverage is 94.11765% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.86%. Comparing base (779b4c7) to head (77e5b49).
Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
src/openscm_zenodo/zenodo.py	90.90%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #12      +/-   ##
==========================================
+ Coverage   79.38%   79.86%   +0.48%     
==========================================
  Files           5        5              
  Lines         291      303      +12     
  Branches       49       50       +1     
==========================================
+ Hits          231      242      +11     
  Misses         42       42              
- Partials       18       19       +1     

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