Custom Serialize/Deserialize

[mehtaphysical]

What do you think about allowing classes to provide custom serialize/deserialize methods?

By adding something like this to serializeStruct

function serializeStruct(schema: Schema, obj: any, writer: any) {
  if (typeof obj.borshSerialize === 'function') {
    obj.borshSerialize(writer);
    return;
  }
.....
}
.....

function deserializeStruct(
  schema: Schema,
  classType: any,
  reader: BinaryReader
) {
  if(typeof classType.borshDeserialize) {
    classType.borshDeserialize(reader);
    return;
  }
....
}

we could then do this:

export class PublicKey {
    keyType: KeyType;
    data: Uint8Array;

    static borsheDeserialize(reader: BinaryReader) {
        reader.readU8
    }

    static borshDeserialize(reader: BinaryReader): PublicKey {
        const keyType = reader.readU8();

        let data;
        if(keyType === KeyType.ED25519) {
            data = reader.readFixedArray(32);
        } else if(keyType === KeyType.SECP256k1) {
            data = reader.readFixedArray(64);
        }

        return new PublicKey({ keyType, data });
    }

    borshSerialize(writer: BinaryWriter) {
        writer.writeU8(this.keyType);
        writer.writeFixedArray(this.data);
    }
}

If this looks good I'm happy to implement it and submit a PR.