Support a non-string based EncoderStream/DecoderStream

[bpasero]

Referring to:

iconv-lite/lib/index.d.ts

Lines 33 to 41 in 148b6bc

	export interface EncoderStream {
	write(str: string): Buffer;
	end(): Buffer | undefined;
	}
	export interface DecoderStream {
	write(buf: Buffer): string;
	end(): string | undefined;
	}

I am not sure why we cannot work without strings in these methods and thus avoid having to create strings while talking to the library. Imho everything here should be Uint8Array based and not string based at all.

[bpasero]

Maybe as an alternative, string | Buffer could be supported, similar to how node.js streams support both.

[ashtuchkin]

This is in line with StreamDecoder in Node.js and TextDecoder/TextEncoder in WHATWG Encodings standard. Conceptually encoding/decoding is a conversion between bytes and strings and in vast majority of cases it makes sense to expose strings to clients. In rare cases where you convert from bytes in encoding A to bytes in encoding B, we recommend just calling encode(decode()) or piping the streams.

Also, btw, Node.js streams can also work with strings just fine, using "object" mode.