feat: add thousands separator

[vlopezferrando]

Add thousands separator (1_000_000) to numbers (ints and floats, positive or negative).

Limitations:

• A max number of 4 underscores are added (the implementation has a copy-pasted regex, which may be improved with some kind of recursive logic).

[morgante]

I'm pretty sure we could do this generically without recursion, using either a more complex regex or a split of some sort.

[morgante]

This is another example of the anti-pattern (maybe we should put this in the docs). If a variable is immediately restricted after assignment, start with the restriction.

Suggested change

	`$number` where {
	$number <: or { integer(), float() },
	or { integer(), float() } as number where {

[vlopezferrando]

Fixed.

[vlopezferrando]

Would it be better if the pattern just added one underscore?

1000 -> 1_000
1000000 -> 1000_000
1000_000 -> 1_000_000

Then, if applied multiple times, it would yield the right output no matter how long the number is.