Add changelog for MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
diff --git a/ChangeLog.d/psa-builtin-keys-implementation.txt b/ChangeLog.d/psa-builtin-keys-implementation.txt
new file mode 100644
index 0000000..66ba77d
--- /dev/null
+++ b/ChangeLog.d/psa-builtin-keys-implementation.txt
@@ -0,0 +1,4 @@
+Features
+   * Added support for built-in driver keys through the PSA opaque crypto
+     driver interface. Refer to the documentation of
+     MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS for more information.