Java Object interopt changed in Scala 2.13.0

This is more just an advisory issue that could be updated and released if older versions like Scala 2.11 and 2.12 get dropped.

- [X] Scala 2.11 dropped
- [ ] Scala 2.12 dropped

Change in Scala 2.13: https://github.com/scala/scala/pull/7966

Code affected: https://github.com/ekrich/sconfig/blob/master/sconfig/shared/src/main/scala/org/ekrich/config/impl/SimpleConfigList.scala#L270

Potential change:

From: `override def toArray[T](a: Array[T with Object]): Array[T with Object] =???`
To: `override def toArray[T <: Object](a: Array[T]): Array[T] = ???`

Edit: or `AnyRef` for `Object`.

Start at sconfig/shared/src/main/scala/org/ekrich/config/impl/SimpleConfigList.scala around line 270 and compare the current toArray signature with the Scala 2.13 change linked in the issue. Check whether Scala 2.12 support has been dropped before deciding which signature is appropriate; done means updating the affected declaration consistently with the supported Scala versions.

Written by the indexing model from the issue text.