Incorrect type for (js.type = "Date")

[NameFILIP]

Thrift definition:

1: optional i64 (js.type = "Date") timestampMs;

Generated type:

timestampMs?: ?string,

while it should be:

timestampMs?: ?string | ?number,

According to https://github.com/thriftrw/thriftrw/blob/master/annotations.md#timestamps

will accept an ISO-8601 timestamp or milliseconds since the epoch (as returned by Date.now())