[docs] Add security policy

[patrick-ogrady]

No description provided.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.50%. Comparing base (2ea78c7) to head (a5505b0).
Report is 2 commits behind head on main.

@@           Coverage Diff           @@
##             main      #20   +/-   ##
=======================================
  Coverage   61.50%   61.50%           
=======================================
  Files          23       23           
  Lines        3403     3403           
=======================================
  Hits         2093     2093           
  Misses       1310     1310           

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