Update ML and contrib training data docs

[MarkDavidson]

What Changed:

1. Added documentation about adding your own ML Model
2. Added documentation about contributing training data

Known Limitations:

1. None

[codecov]

Codecov Report

Merging #94 (6cf922d) into master (a4d874c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #94   +/-   ##
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  Coverage   94.29%   94.29%           
=======================================
  Files          17       17           
  Lines         824      824           
=======================================
  Hits          777      777           
  Misses         47       47           

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[sonarcloud]

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