Configure the schema format if the email validator is set

[mcorbin]

This commit set the schema format to "email" if the email validator is
set on a field.

[codecov]

Codecov Report

Merging #83 (923277f) into master (923277f) will not change coverage.
The diff coverage is n/a.

❗ Current head 923277f differs from pull request most recent head c4349ba. Consider uploading reports for the commit c4349ba to get more accurate results

@@           Coverage Diff           @@
##           master      #83   +/-   ##
=======================================
  Coverage   94.91%   94.91%           
=======================================
  Files           7        7           
  Lines         964      964           
=======================================
  Hits          915      915           
  Misses         33       33           
  Partials       16       16           

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