Add prefix: markerdb

[nagutm]

PubMed: https://pubmed.ncbi.nlm.nih.gov/39535054/
Database: https://markerdb.ca/

This pull request curates a new prefix markerdb which provides identifiers for various molecular biomarkers.

This resource is curated without a uri_format since the number in the URL for individual entries seems irrelevant and unrelated to the MarkerDB ID associated with each biomarker.

[bgyori]

I fixed the curations table which had the wrong PMID in it, added the Github handle for the contact, and extended the description.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.61%. Comparing base (8950e70) to head (2482cd8).
Report is 225 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1330      +/-   ##
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+ Coverage   42.51%   46.61%   +4.09%     
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  Files         117      118       +1     
  Lines        8327     8292      -35     
  Branches     1963     1363     -600     
==========================================
+ Hits         3540     3865     +325     
+ Misses       4582     4241     -341     
+ Partials      205      186      -19     

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