inline List Mode
How should inline lists be serialized?
If ListMode.SingleLine, inline lists are always serialized on a single line.
If ListMode.MultiLine, inline lists are always serialized with one element per line, as long as the TOML spec allows it.
If ListMode.Adaptive, inline lists are serialized with one element per line only if they contain one or more list or table, as long as the TOML spec allows it.
Default: ListMode.Adaptive