Add pre-commit hook for validating configuration

[peterb-oanda]

Add pre-commit hook configuration for validating CircleCI config files

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@6f8e97e). Click here to learn what that means.
Patch has no changes to coverable lines.

❗ Current head eb9f60f differs from pull request most recent head 2c60dac. Consider uploading reports for the commit 2c60dac to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #655   +/-   ##
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  Coverage           ?   27.48%           
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  Files              ?       40           
  Lines              ?     4500           
  Branches           ?        0           
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  Hits               ?     1237           
  Misses             ?     3113           
  Partials           ?      150           

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