Unicode letters break type name

[Timeroot]

When a type has a unicode letter (like Δ) in the name, this "breaks" the name and the hightlight stops before. I'm guessing this is some issue in what letters are viewed as continuations of type names. As an example, you can see this code in Roots.jl:

https://github.com/JuliaMath/Roots.jl/blob/master/src/Derivative/halley_like.jl#L131

struct ChebyshevLike <: AbstractΔMethod end

which highlights as

[pfitzseb]

This seems like a bug in the GH highlighter, specifically. Your examples is highlighted correctly in both VS Code and Atom (I've also added a test for that in #260).