feat: allow to specify icon size

[gregberge]

BREAKING CHANGE: using --icon as latest arg now requires "--"

Fix #571

[vercel]

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[codecov]

Codecov Report

Merging #625 (483560d) into main (6ba16a3) will increase coverage by 0.10%.
The diff coverage is 90.90%.

@@            Coverage Diff             @@
##             main     #625      +/-   ##
==========================================
+ Coverage   89.12%   89.23%   +0.10%     
==========================================
  Files          32       32              
  Lines         699      715      +16     
  Branches      221      233      +12     
==========================================
+ Hits          623      638      +15     
- Misses         75       76       +1     
  Partials        1        1              

Impacted Files	Coverage Δ
packages/core/src/config.ts	100.00% <ø> (ø)
...ckages/babel-plugin-svg-em-dimensions/src/index.ts	89.28% <85.71%> (-5.46%)	⬇️
packages/babel-preset/src/index.ts	95.34% <100.00%> (+3.68%)	⬆️

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