write fails on large dataframes

[0xYUANTI]

hi :)

as indicated in the Tables.jl docs, for large dataframes (>10k columns), Tables.Schema stores its values in
.storenames and .storedtypes instead of the type parameters. This needs to be taken into account in,
eg. makeschema in write.jl and possibly other places.

EDIT: I just added if isnothing(names) names_ = sch.names else names_ = names end
(and replace names with names_ below) in my checkout and that fixed writing for me.