Fix variants with <digit>.</digit> are extracted correctly

[RobinMalfait]

This PR fixes an issue where if you use a number with a decimal in a variant then it wasn't picked up correctly.

E.g.:

<div class="2xl:flex 1.5xl:flex"></div>
            ^^^^^^^^                        Picked up
                     ^^^^^^^^^^             Not picket up

This PR fixes that behavior by applying the same rules for utilities where a . is valid if it is surrounded by numbers.

Test plan

1. Added test to ensure this is picked up
2. Existing tests pass
3. Ran the extractor on a real example with the following results:

Before	After

They are crossed out just because it's not a default value we know in the system, but you can see that the 1. part is also extracted now.

Fixes: #17148

[thecrypticace]

lgtm (aside from the comment)