Fix CompressionTypes.Snappy naming for KafkaJS compatibility

Rename SNAPPY to Snappy to match the original KafkaJS API naming
convention, ensuring backward compatibility for users migrating
from kafkajs. Also fixes mismatch between TypeScript types and
JavaScript implementation.

Author: VLZH

lib/kafkajs/_producer.js

@@ -34,7 +34,7 @@ const ProducerState = Object.freeze({
 const CompressionTypes = {
   None: 'none',
   GZIP: 'gzip',
-  SNAPPY: 'snappy',
+  Snappy: 'snappy',
   LZ4: 'lz4',
   ZSTD: 'zstd',
 };