Update release notes for PR #23

Author: ponylang-main

.release-notes/next-release.md

@@ -10,3 +10,16 @@ Previously, when a `TCPConnectionNotify` wrapped by `SSLConnection` returned `fa
 
 `SSLConnection` now properly propagates the wrapped notify's `received` return value to `TCPConnection`, allowing the backpressure/yield mechanism to work through SSL connections.
 
+## Add variable-length output support to SHAKE digests
+
+The `shake128` and `shake256` constructors on `Digest` now accept an optional `size` parameter that controls the output length in bytes. The defaults match the previous fixed sizes (16 bytes for SHAKE128, 32 for SHAKE256), so existing code is unaffected.
+
+Variable-length output requires OpenSSL 3.0.x. On OpenSSL 1.1.x, the default size is always used regardless of the parameter value.
+
+```pony
+// 64-byte SHAKE256 digest (OpenSSL 3.0.x)
+let d = Digest.shake256(64)
+d.append("input data")?
+let hash: Array[U8] val = d.final()  // 64 bytes
+```
+