fix(Dropdown): allow defaultValue to be a boolean

[leonardosul]

A previous fix allowed using booleans as options for dropdowns. This adds the ability to also use a boolean as the defaultValue for a dropdown.

Booleans currently work as default value for dropdowns, but this change removes annoying console errors about propType errors.

[welcome]

💖 Thanks for opening this pull request! 💖

Here is a list of things that will help get it across the finish line:

• Run yarn lint locally to catch formatting errors. This will fix some errors automatically, commit and push any changes.
• Run yarn test locally to catch errors. This ensures all components still behave as they should.
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• Include tests when adding/changing behavior.

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[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@1d795bc). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2972   +/-   ##
=========================================
  Coverage          ?   99.81%           
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  Files             ?      163           
  Lines             ?     2738           
  Branches          ?        0           
=========================================
  Hits              ?     2733           
  Misses            ?        5           
  Partials          ?        0

Impacted Files	Coverage Δ
src/modules/Dropdown/Dropdown.js	100% <ø> (ø)

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[welcome]

Congrats on merging your first pull request! 🎉🎉🎉

[levithomason]

Released in [email protected].