Fix interpolate expression

[lhapaipai]

Hi, and thank you for providing these ready-to-use styles.

This PR fixes some linear interpolation expressions to align with the MapLibre specification:
https://maplibre.org/maplibre-style-spec/expressions/#interpolate

[hyperknot]

Thanks for your work @lhapaipai and sorry for the late reply!

Do you know why the linter tool doesn't raise it as a warning? Or was this changed recently in the specs?

[lhapaipai]

Hi @hyperknot !
No problem,

Maybe because if a second argument is passed for the linear interpolation, it’s simply not parsed.

Source code

I ran into the issue again because I needed to type the style, and the typing is stricter.

type InterpolationSpecification =
    | ['linear']
    | ['exponential', number]
    | ['cubic-bezier', number, number, number, number]