chore: Update and unify expandToViewport API documentation

[timogasda]

Description

Update expandToViewport documentation to be more clear.

Related links, issue #, if available: AWSUI-21409,STUtACqqlwLT

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (7a9c0b7) 93.48% compared to head (a79d040) 93.48%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1383   +/-   ##
=======================================
  Coverage   93.48%   93.48%           
=======================================
  Files         624      624           
  Lines       16796    16796           
  Branches     5558     5558           
=======================================
  Hits        15701    15701           
  Misses       1022     1022           
  Partials       73       73           

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