The current extended JSON parser uses a JSON parser that can only decode JSON using callbacks. The new encoder and decoder design requires a parser that acts like a state machine.
The standard library json.Decoder provides the primitives to do this via the Token method. Build an Extended JSON parser on top of the json.Decoder that operates on a slice of bytes. The standard library json.Decoder does not provide the promise nor the necessary peek functionality to create a non-complex extended JSON parser. Since we will not need anything more than a JSON scanner that can peek inside an object, implement a JSON parser that is RFC 8259 compliant.
Additionally, implement an extended JSON ValueReader on top of this Extended JSON parser and JSON ValueWriter.