add readme file for the thread br app example

Author: wqx6

examples/thread-br-app/esp32/README.md

@@ -0,0 +1,82 @@
+# Matter ESP32 Thread Border Router Example
+
+A prototype application that demonstrates OpenThread Border Router on ESP32-S3 + ESP32-H2
+Thread Border Router DevKit Board.
+
+Please
+[setup ESP-IDF and CHIP Environment](../../../docs/guides/esp32/setup_idf_chip.md)
+and refer
+[building and commissioning](../../../docs/guides/esp32/build_app_and_commission.md)
+guides to get started.
+
+---
+
+-   [OpenThread Border Router DevKit Board](#openthread-border-router-board)
+-   [OpenThread RCP](#openthread-rcp)
+-   [OpenThread CLI](#openthread-cli)
+-   [Setup Thread Network](#setup-thread-network)
+-   [Commissioning Thread End Devices](#commissioning-thread-end-devices)
+
+---
+
+### Thread Border Router Board
+
+The ESP Thread border router board provides an integrated module of an ESP32-S3 and an ESP32-H2.
+
+![br_dev_kit](./image/esp-thread-border-router-board.png)
+
+### OpenThread RCP
+
+We need to flash an OpenThread RCP(Radio Co-Processor) on ESP32-H2 of the Border Router Board before setting
+up the Thread Border example. Connect the USB1 port of the Border Router Board to your host machine. Then
+build and flash the RCP firmware
+
+```
+cd $IDF_PATH/examples/openthread/ot_rcp
+idf.py set-target esp32-h2
+idf.py build
+idf.py -p {port} erase-flash flash
+```
+
+### OpenThread CLI
+
+After you build this example and flash it to the ESP32-S3 of Border Router Board, you can access a standard
+OpenThread CLI via the device console with a `matter otcli` prefix.
+
+For instance, you can get the state:
+```
+> matter otcli state
+Detached
+Done
+```
+
+### Setup Thread Network
+
+You can choose to setup Thread network with the [OpenThread CLI](#openthread-cli).
+
+```
+> matter otcli dataset set active <dataset-tlvs>
+> matter otcli dataset commit active
+> matter otcli ifconfig up
+> matter otcli thread start
+```
+
+Or you can send SetActiveDatasetRequest command to the Thread BR after commissioning it as a
+Matter-Over-Wi-Fi device to setup the Thread network.
+
+```
+./chip-tool pairing ble-wifi 1 <ssid> <password> 20202021 3840
+./chip-tool generalcommissioning arm-fail-safe 180 1 1 0
+./chip-tool threadborderroutermanagement set-active-dataset-request hex:<dataset-tlvs> 1 1 1
+```
+
+The Thread BR with enable the Thread network interface and start Thread network after it receives
+SetActiveDatasetRequest command.
+
+### Commissioning Thread End Devices
+
+After setting up the Thread network, you can commission a Thread End-device to the Thread network.
+
+```
+./chip-tool pairing ble-wifi 2 hex:<dataset_tlvs> <pincode> <discriminator>
+```