fix(Dropdown): retain focus on the input if the Dropdown receives a click

[jongsue]

fix #3346

[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.
• Run yarn start to run the doc site locally and try a few pages, ensuring everything is in good working order.
• Include tests when adding/changing behavior.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[codecov-io]

Codecov Report

Merging #3422 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3422      +/-   ##
==========================================
+ Coverage   99.89%   99.92%   +0.03%     
==========================================
  Files         172      172              
  Lines        2835     2837       +2     
==========================================
+ Hits         2832     2835       +3     
+ Misses          3        2       -1

Impacted Files	Coverage Δ
src/modules/Dropdown/Dropdown.js	100% <100%> (+0.23%)	⬆️
src/modules/Checkbox/Checkbox.js	100% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a4bf431...4b5032b. Read the comment docs.

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉

[levithomason]

Released in [email protected].