Add MariaDB to README.md

[robertsilen]

Any reason not to add MariaDB to the README? Suggesting to add it with this PR. Cheers, Robert

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[vangent]

See suggestion.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.25%. Comparing base (5695484) to head (d654e43).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3509      +/-   ##
==========================================
+ Coverage   73.24%   73.25%   +0.01%     
==========================================
  Files         113      113              
  Lines       15052    15052              
==========================================
+ Hits        11025    11027       +2     
+ Misses       3262     3260       -2     
  Partials      765      765              

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