fix(google_fonts): handle unnamed @font-face subsets

[ras0q]

Description

When using Japanese fonts such as Zen Maru Gothic, the Japanese subset is not installed and will not be applied.

Since font-face does not necessarily have a subset name, I modified the regular expression.

e.g. https://fonts.googleapis.com/css2?family=Zen+Maru+Gothic:wght@700&display=swap

reproduction: https://github.com/ras0q/lume-repro-google-fonts-missing-subsets/tree/main/after

Related Issues

Fixes #784

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[oscarotero]

Oh, good catch! Thank you!
(don't worry about the failing tests)