feat(icons): use rem on icons

[matthprost]

Summary

Type

• Feature

Summarise concisely:

What is expected?

Migrate icons on new rem size instead of px.

[changeset-bot]

🦋 Changeset detected

Latest commit: 51bb702

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@ultraviolet/icons	Minor
@ultraviolet/plus	Patch
@ultraviolet/ui	Patch
@ultraviolet/form	Patch

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.45%. Comparing base (4d8a5b5) to head (51bb702).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4602      +/-   ##
==========================================
- Coverage   87.60%   87.45%   -0.16%     
==========================================
  Files         335      335              
  Lines       12808    12812       +4     
  Branches     3532     3534       +2     
==========================================
- Hits        11221    11205      -16     
- Misses       1587     1607      +20     

see 8 files with indirect coverage changes

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