Add PSA to README

[davidgrisham]

My company recently started using this package for our NodeJS clients when integrating Confluent's Schema Registry into our infrastructure. We recently ran into issues with Protobuf messages serialized by Confluent's Go client that revealed incompatibilities with the wire format expected by this library. After this discovery I realized this was a known issue.

As this is the most prominent JS client for Confluent's schema registry, I believe it was easy for us to misinterpret this as a fully compatible client. I'm currently working to rectify this on our end, and hope to contribute to this package to fix the issue for others across the board. In the meantime, I've updated the README with the details I found as I was coming to understand these things, as they are crucial for anyone looking to integrate this into their infrastructure.

[davidgrisham]

cc @Nevon

[xav-ie]

hahahahahahah. This was my draft issue I was going to file. It seems like we walked similar paths.
I am not sure why this is happening, when the docs say that you can do this:

import { SchemaRegistry, SchemaType } from '@kafkajs/confluent-schema-registry';
const registry = new SchemaRegistry({ host: 'http://localhost:8081' })
const { id } = await registry.register({
  type: SchemaType.PROTOBUF,
  // 2322: Type 'SchemaType.PROTOBUF' is not assignable to type 'SchemaType.AVRO | "record"'.
  schema: protoString,
  subject: 'orders-value'
});

node version 20.11.0. using npm. package.json:

    "@kafkajs/confluent-schema-registry": "^3.3.0",

Adding ts-ignore, I can finally run, but I get:

ConfluentSchemaRegistryError: not implemented yet
    at ProtoHelper.getSubject (/home/x/Outsmartly/local-kafka/node_modules/@kafkajs/confluent-schema-registry/src/ProtoHelper.
ts:22:11)
    at SchemaRegistry.register (/home/x/Outsmartly/local-kafka/node_modules/@kafkajs/confluent-schema-registry/src/SchemaRegis
try.ts:128:24)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async produceTopic (/home/x/Outsmartly/local-kafka/src/produce-topic.ts:129:20)
    at async /home/x/Outsmartly/local-kafka/src/produce-topic.ts:185:5

Why do the docs say otherwise? Happy to make PR just mentioning this. Has anyone seen https://github.com/konqi/schematic-kafka? Seems to have protobuf support, and it is also under MIT license, I also saw #258 . It looks like David is doing great work there.