[k32w0] Add OTA encryption info in contact sensor README

Contact sensor uses some gn args to enable OTA encryption.
This means that an upcoming OTA image must be encrypted
with the same key provided by chip_with_ota_key.

Signed-off-by: marius-alex-tache <marius.tache@nxp.com>

Author: marius-alex-tache

examples/contact-sensor-app/nxp/k32w/k32w0/README.md

@@ -14,42 +14,42 @@ network.
 
 <hr>
 
--   [CHIP K32W061 Contact Sensor Example Application](#chip-k32w061-contact-sensor-example-application)
-    -   [Introduction](#introduction)
-        -   [SE051H Secure Element](#se051h-secure-element)
-        -   [Bluetooth LE Advertising](#bluetooth-le-advertising)
-    -   [LIT ICD Active Mode](#lit-icd-active-mode)
-        -   [Bluetooth LE Rendezvous](#bluetooth-le-rendezvous)
-        -   [Thread Provisioning](#thread-provisioning)
-    -   [Device UI](#device-ui)
-        -   [No expansion board](#no-expansion-board)
-    -   [Building](#building)
-    -   [Long Idle Time ICD Support](#long-idle-time-icd-support)
-        -   [Overwrite board config files](#overwrite-board-config-files)
-        -   [Known issues building](#known-issues-building)
-    -   [Rotating device id](#rotating-device-id)
-    -   [Manufacturing data](#manufacturing-data)
-    -   [Flashing and debugging](#flashing-and-debugging)
-    -   [Pigweed tokenizer](#pigweed-tokenizer)
-        -   [Detokenizer script](#detokenizer-script)
-        -   [Notes](#notes)
-        -   [Known issues tokenizer](#known-issues-tokenizer)
-    -   [NXP Ultrafast P256 ECC Library](#nxp-ultrafast-p256-ecc-library)
-        -   [Building steps](#building-steps)
-    -   [Tinycrypt ECC library](#tinycrypt-ecc-library)
-        -   [Building steps](#building-steps-1)
-    -   [OTA](#ota)
-        -   [Writing the SSBL](#writing-the-ssbl)
-        -   [Features](#features)
-            -   [Multi image](#multi-image)
-            -   [Simple hash verification](#simple-hash-verification)
-        -   [Writing the PSECT](#writing-the-psect)
-        -   [Writing the application](#writing-the-application)
-        -   [OTA Testing](#ota-testing)
-        -   [Known issues ota](#known-issues-ota)
-    -   [Low power](#low-power)
-        -   [Known issues low power](#known-issues-low-power)
-    -   [Removing SSBL Upgrade Region](#removing-ssbl-upgrade-region)
+- [CHIP K32W061 Contact Sensor Example Application](#chip-k32w061-contact-sensor-example-application)
+  - [Introduction](#introduction)
+    - [SE051H Secure Element](#se051h-secure-element)
+    - [Bluetooth LE Advertising](#bluetooth-le-advertising)
+  - [LIT ICD Active Mode](#lit-icd-active-mode)
+    - [Bluetooth LE Rendezvous](#bluetooth-le-rendezvous)
+    - [Thread Provisioning](#thread-provisioning)
+  - [Device UI](#device-ui)
+    - [No expansion board](#no-expansion-board)
+  - [Building](#building)
+  - [Long Idle Time ICD Support](#long-idle-time-icd-support)
+    - [Overwrite board config files](#overwrite-board-config-files)
+    - [Known issues building](#known-issues-building)
+  - [Rotating device id](#rotating-device-id)
+  - [Manufacturing data](#manufacturing-data)
+  - [Flashing and debugging](#flashing-and-debugging)
+  - [Pigweed tokenizer](#pigweed-tokenizer)
+    - [Detokenizer script](#detokenizer-script)
+    - [Notes](#notes)
+    - [Known issues tokenizer](#known-issues-tokenizer)
+  - [NXP Ultrafast P256 ECC Library](#nxp-ultrafast-p256-ecc-library)
+    - [Building steps](#building-steps)
+  - [Tinycrypt ECC library](#tinycrypt-ecc-library)
+    - [Building steps](#building-steps-1)
+  - [OTA](#ota)
+    - [Writing the SSBL](#writing-the-ssbl)
+    - [Features](#features)
+      - [Multi image](#multi-image)
+      - [Simple hash verification](#simple-hash-verification)
+    - [Writing the PSECT](#writing-the-psect)
+    - [Writing the application](#writing-the-application)
+    - [OTA Testing](#ota-testing)
+    - [Known issues ota](#known-issues-ota)
+  - [Low power](#low-power)
+    - [Known issues low power](#known-issues-low-power)
+  - [Removing SSBL Upgrade Region](#removing-ssbl-upgrade-region)
 
 ## Introduction
 
@@ -730,9 +730,14 @@ Please see more in the
 Here is an example that generates an OTA image with application update TLV:
 
 ```
-./scripts/tools/nxp/ota/ota_image_tool.py create -v 0xDEAD -p 0xBEEF -vn 42021 -vs "1.0" -da sha256 --app-input-file chip-k32w0x-contact-example.bin chip-k32w0x-contact-example.ota
+./scripts/tools/nxp/ota/ota_image_tool.py create -v 0xDEAD -p 0xBEEF -vn 2 -vs "2.0" -da sha256 --enc_enable --input_ota_key "1234567890ABCDEFA1B2C3D4E5F6F1B4" --app-input-file chip-k32w0x-contact-example.bin chip-k32w0x-contact-example.ota
 ```
 
+Please note the two options `--enc_enable` and `--input_ota_key`, which are
+mandatory when `chip_with_ota_encryption=1`. The value of `--input_ota_key` must
+match the value of `chip_with_ota_key`. See `args.gni` for the default gn
+configuration.
+
 A note regarding OTA image header version (`-vn` option). An application binary
 has its own software version, given by
 `CHIP_DEVICE_CONFIG_DEVICE_SOFTWARE_VERSION` (`42020` by default), which can be