Allow `em` for dimension token

[lukasoppermann]

Before starting

• I have searched existing issues and there is not already an open issue on the subject.

Summary

Add em to the supported values for dimension tokens.

In contrast to px and rem, em are related to the current text size. This behavior can not be easily replicated with rem or px.

However in some cases, like inline code in text blocks of different sizes, icons that are placed inside of text, etc. it is important to use em as you would otherwise need to define additional tokens for each situation.

Version

2025.10 (current stable version)

Problem & motivation

No response

Prior art

No response

Pros & cons

No response

Alternatives

No response

Required

• I have read and agree to abide by the CODE_OF_CONDUCT

[dgtlntv]

I have also run into the issue. I wanted my letter spacing to be relative to the font size (so using em). With only rem and px being allowed I'd have to create a letter spacing token for every font size token I have.