Add whitelist to seagull stealing

[johalun]

In our use case, the options to either disable stealing completely, or blacklist certain foods is not enough. We're using Spice Of Life - Valheim in our pack and would like it if there was a whitelist so that we can enable stealing for just some select simple food items.

Currently, all players just avoid beaches because the seagull which unfortunate so we had to disable stealing. However, it's a great mechanic and seagulls adds a lot of atmosphere so I wish this was more configurable using a whitelist.

Thanks!