Add extension to make TimeArray JSON3 serializable

[ValentinKaisermayer]

The main problem is that a TimeArray is a parametric type, which is difficult to implement, see.

The meta::Any field is not serializable as a JSON in any case.
JSON.json even results in a stack overflow error.

This does work, but still makes the assumption that the timestamps are DateTime.
They can be anything: Date, DateTime, TimeZones.ZonedDateTime, TimesDates.TimeDate, TimesDates.TimeDateZone

StructTypes.StructType(::Type{<:TimeSeries.TimeArray}) = StructTypes.CustomStruct()
function StructTypes.lower(x::TimeSeries.TimeArray)
    return Dict(
        "timestamp" => TimeSeries.timestamp(x),
        "values" => [TimeSeries.values(x[c]) for c in TimeSeries.colnames(x)],
        "colnames" => String.(TimeSeries.colnames(x)),
    )
end
function StructTypes.construct(::Type{TimeSeries.TimeArray}, x)
    return TimeSeries.TimeArray(
        Dates.DateTime.(x["timestamp"]),
        reduce(hcat, x["values"]), 
        Symbol.(x["colnames"]),
    )
end