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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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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