docs(README.md): fix formatting

[klunico]

No description provided.

[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-commenter]

Codecov Report

Merging #3958 into master will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3958      +/-   ##
==========================================
- Coverage   99.84%   99.84%   -0.01%     
==========================================
  Files         183      178       -5     
  Lines        3157     3150       -7     
==========================================
- Hits         3152     3145       -7     
  Misses          5        5              

Impacted Files	Coverage Δ
src/modules/Dropdown/Dropdown.js	100.00% <0.00%> (ø)
src/modules/Transition/Transition.js	100.00% <0.00%> (ø)
src/behaviors/Visibility/Visibility.js	100.00% <0.00%> (ø)
src/modules/Transition/TransitionGroup.js	100.00% <0.00%> (ø)
...ddons/TransitionablePortal/TransitionablePortal.js	100.00% <0.00%> (ø)
src/modules/Transition/utils/wrapChild.js
src/modules/Dropdown/utils/getSelectedIndex.js
src/modules/Dropdown/utils/getMenuOptions.js
src/modules/Transition/utils/childMapping.js
src/modules/Transition/utils/computeStatuses.js
... and 2 more

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[welcome]

Congrats on merging your first pull request! 🎉🎉🎉