feat(Sticky): add styleElement prop

[Wattenberger]

A small change to preserve any styles passed to Sticky to fix #2908

[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 #3202 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3202      +/-   ##
==========================================
+ Coverage   99.92%   99.92%   +<.01%     
==========================================
  Files         169      169              
  Lines        2801     2802       +1     
==========================================
+ Hits         2799     2800       +1     
  Misses          2        2

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

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[layershifter]

@Wattenberger thank you, I made some changes 👍

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉