docs(IconExampleFitted): better demonstrate fitted

[levithomason]

The current example is a poor indicator of what "fitted" is doing. Improved the layout to better show the use of margins:

Before

After

[codecov-io]

Codecov Report

Merging #3058 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3058   +/-   ##
=======================================
  Coverage   99.96%   99.96%           
=======================================
  Files         163      163           
  Lines        2738     2738           
=======================================
  Hits         2737     2737           
  Misses          1        1

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