UX-292 Add Button.Icon

[jonambas]

Closes #522

What Changed

• Adds new Button.Icon component to handle vertically centering icons easily inside buttons

How To Test or Verify

• Run storybook and visit http://localhost:9001/?path=/story/action-button--icon

PR Checklist

• Add the correct type label
• Pull request approval from #uxfe or #design-guild

[codecov]

Codecov Report

Merging #576 into rc/4.1.0 will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           rc/4.1.0     #576      +/-   ##
============================================
+ Coverage     93.36%   93.39%   +0.03%     
============================================
  Files           128      129       +1     
  Lines          1688     1696       +8     
============================================
+ Hits           1576     1584       +8     
  Misses          112      112              

Impacted Files	Coverage Δ
packages/matchbox/src/components/Button/Button.js	100.00% <100.00%> (ø)
packages/matchbox/src/components/Button/Icon.js	100.00% <100.00%> (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 8d5ce4e...b51d742. Read the comment docs.

[logansparlin]

Looks good