@nuxt/content class syntax not working

[watzon]

Describe the bug
@nuxt/content allows you to define classes on an object using the [span]{.some-class} syntax. Windi seems to be ignoring these classes since they are prefixed with a period.

To Reproduce
Steps to reproduce the behavior:

1. Create a nuxt project using @nuxt/content
2. In your content markdown use the above syntax.

Expected behavior
Windi's extractor should be able to correctly extract the classes, even when they're formatted as .some-class