Fix highlighting of base 10 numbers

[asottile]

This was incorrectly highlighting the following:

ref: 3.8.3  # should be a string, highlighted as a number

[asottile]

@infininight this patch is small and subtle, would you be able to review?

[geekley]

Weirdly the dot in the regex is ... official? https://yaml.org/type/float.html

[-+]?([0-9][0-9_]*)?\.[0-9.]*([eE][-+][0-9]+)? (base 10)

This allows even weird things like 1.....1
Don't ask me why.

[asottile]

I suspect it's a mistake in the spec there -- it's not implemented that way in libyaml

[geekley]

In fact, it's highly questionable, since one of the examples doesn't even match the regex (and has a typo):

exponentioal: 685.230_15e+03

[geekley]

I don't know whether those "type" pages should be "official" or not ... they're "drafts" and from a previous version of the spec.
The 1.2.2 spec has a different regex in the recommended Core Schema
[-+]? ( \. [0-9]+ | [0-9]+ ( \. [0-9]* )? ) ( [eE] [-+]? [0-9]+ )?
This all is too confusing. Same with what counts as a boolean.
I don't know much about YAML, but I already know I don't like it 😆

[geekley]

Oh. I suspect the repeatable . was supposed to be a repeatable _. This makes sense based on that example, which would match in this case. I'll try reporting this on yaml spec repo.