Jiri

@ds300 How would you implement a body of `process` function? ``` export function process(text: T): T extends string ? string : null { return text === null ? null :...

Works when you make an instance of `Encoder.Derived` instead of `Encoder` (see https://scastie.scala-lang.org/K8JzCDUPQayyHDoNpA6CUA). I don't really understand the purpose of `Dervied extends Encoder` type. Maybe `Encoder` on its own would...