Upgrade Makie

Makie v0.18.0 brings a lot of breaking changes that negatively affect LarvaTagger.jl.

A first error is:

LoadError: MethodError: no method matching getindex(::typeof(Makie.current_backend))

from expression const wgl = startswith(string(Makie.current_backend[]), "WGL")

Makie.current_backend was a Ref prior to 0.18.0 and is now a function.

Once fixed, we hit more errors that may be linked to #56 (closed).