Splitwise import: wrong date for all bills

Hi,

First of all, love this project and would very much like to migrate from Splitwise.

Tried out the Splitwise import and noticed there is a bug with the date it seems. All imported bills have the same date, the one from the last bill in the Splitwise project.

It happens because of this line: https://gitlab.com/eneiluj/cospend-nc/-/blob/master/lib/Service/ProjectService.php#L4184

Here $timestamp should be replaced with $bill['timestamp']

Kind regards