support for nested structs or lists

[skurfuerst]

Hey,
thanks for your library!

Sometimes I need to configure lists of complex objects, or maps of complex objects - seems this is currently not supported?

so:

type Config struct {
	Clickhouse []ClickHouseConfig
}

or

type Config struct {
	Clickhouse map[string]ClickHouseConfig
}

at least I was not able to supply the values via YAML in these cases :)

All the best and keep up the good work,
Sebastian