Allow multiples of .25 in aspect-* fractions

[RobinMalfait]

This PR reduces the restrictions of the aspect-* utilities when dealing with fractional values.

Up until now, the numbers had to be positive integers, so aspect-1/2 was valid, but aspect-8.5/11 was not.

This PR allows for any multiple of .25 as a valid value, so aspect-8.5/11 is now valid, but aspect-8.3/11 is not, this will still require aspect-[8.3/11] arbitrary value syntax to be valid.

This behavior of allowing multiples of .25 is consistent with other utilities that handle bare values such as w-2.5.

Test plan

1. Existing tests pass
2. Added a test for aspect-8.5/11

Fixes: #19663
Closes: #19680, #19669

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Walkthrough

This pull request adds support for decimal fractions in aspect-ratio utilities. The CHANGELOG documents the addition of multiples of .25 in aspect-* fractions. The validation logic in utilities.ts is updated to accept decimal values by replacing integer-only validation with isValidSpacingMultiplier checks. A test case is added to utilities.test.ts to verify the new aspect-[8.5/11] class generates the correct CSS rule aspect-ratio: 8.5 / 11;.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Allow multiples of .25 in aspect-* fractions' accurately summarizes the main change: relaxing aspect-ratio utility validation to accept decimal values that are multiples of 0.25.
Description check	✅ Passed	The description is well-related to the changeset. It explains the purpose (allowing multiples of .25 in aspect-* utilities), provides context (previous integer-only restriction), and references the test plan and linked issues.
Linked Issues check	✅ Passed	The PR implementation aligns with linked issues #19663, #19680, and #19669. It addresses the core requirement to allow decimal aspect ratios by accepting multiples of 0.25 [#19663, #19680] while maintaining consistency with other utilities accepting bare decimal values.
Out of Scope Changes check	✅ Passed	All changes are in-scope: CHANGELOG.md documents the feature, utilities.ts implements the validation change using isValidSpacingMultiplier for both fraction components, and utilities.test.ts adds the required test case for aspect-8.5/11.

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[shtse8]

Hey @RobinMalfait, thanks for picking this up! Would you mind adding a Co-authored-by credit since I raised the issue and submitted the original PR (#19669)? Would appreciate it 🙏

Co-authored-by: shtse8 <shtse8@gmail.com>