Introduce demo script for PSA hash program

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>

programs/psa/psa_hash_demo.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+#
+# Copyright The Mbed TLS Contributors
+# SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+
+. "${0%/*}/../demo_common.sh"
+
+msg <<'EOF'
+This program demonstrates the use of the PSA cryptography interface to
+compute a SHA-256 hash of a test string using the one-shot API call
+and also using the multi-part operation API.
+EOF
+
+depends_on MBEDTLS_PSA_CRYPTO_C PSA_WANT_ALG_SHA_256
+
+program="${0%/*}"/psa_hash
+
+"$program"
+
+cleanup