Tranform.sizePX DTCG unit value object

[thierryc]

Issue #1501

Description of changes:

Add support for nested value unit object of the DTCG format in tranform.sizePX.

value: {
       value: '24',
       unit: 'px',
},

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[artursopelnik]

Here you could find a workaround for dimension:

https://github.com/amzn/style-dictionary/issues/848#issuecomment-2855874849

[tkgroot]

Just came across this PR and linked issue. For the purpose of completion, linking this one to the issue #1584 as well.