Update frenet.jl

[chelseas]

No description provided.

[coveralls]

Coverage remained the same at 29.27% when pulling beb9f4b on chelseas:master into 67d8259 on sisl:master.

[MaximeBouton]

If you want the comment to show up when the help is toggled (?Frenet, #14 ) , you can add a docstring in front of the type defintion:

"""
My doc
"""
struct MyStruct
end

The docstring supports markdown.
Style guide: https://docs.julialang.org/en/stable/manual/documentation/

[MaximeBouton]

Thanks for this,
It seems like the build is failing because of the last update in sisl/Vec.jl@e0fb7a5 .
I will merge this PR since it is unrelated and submit an issue.