Support for encoding/decoding a sequence of values

[UnknownJoe796]

This PR is intended to be for after #19 might be merged, as it is dependent.

Built explicitly to stream the processing of rows in a CSV effectively. Introduces the following functions to CSV:

// Encodes a sequence of values in a streaming fashion.
fun <T> encodeSequenceToAppendable(serializer: KSerializer<T>, values: Sequence<T>, appendable: Appendable) 

// Begin encoding, gives back a function to add an item.  Useful in conjuction with `suspend`.
@ExperimentalSerializationApi
fun <T> beginEncodingToAppendable(serializer: KSerializer<T>, appendable: Appendable): (T) -> Unit

// Decodes values as a sequence for doing streaming operations.
@ExperimentalSerializationApi
fun <T> decodeSequenceFromReader(deserializer: KSerializer<T>, reader: Reader): Sequence<T>

// A safer version of the above where the reader is closed by the function.
fun <T> decodeFromReaderUsingSequence(deserializer: KSerializer<T>, reader: Reader, handler: (Sequence<T>) -> Unit)

I acknowledge this API as needing additional review moreso than my other PR, which simply introduced using Reader and Appendable. We need to make sure the introduced API does not cause confusion or subtle issues.

This is the same as a previous PR but from a fork where I can allow editing from maintainers.

[brudaswen]

Thanks for the contribution. I changed the API a bit, but it should allow the same streaming support.