move embedded tutorials out of protocol tree

tutorials/esp32/uart-bridge/README.md

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+# A UART to network bridge for ESP32
+
+![](../../uart-bridge/screenshots/dashboard.png)
+
+- See detailed tutorial at https://mongoose.ws/tutorials/esp32/uart-bridge/
+
+## Flash pre-built firmware
+
+You can flash a pre-built firmware to the ESP32 device using the following
+instructions:
+
+1. Connect your ESP32 device to the workstation. It should be accessible
+   via a serial port
+2. Download and unzip ESP32 flashing tool from https://mongoose.ws/downloads/esputil.zip
+3. Download a prebuilt firmware https://mongoose.ws/downloads/uart-bridge.hex into the unzipped directory
+4. Start command prompt (or terminal on Mac/Linux). Run `cd
+  PATH/TO/esputil`  to go into the unzipped `esputil/` directory. After that, run
+  the following command (change `COMPORT` to the board's serial port):
+
+  | OS      | Command |
+  | ------- | ------- |
+  | Windows | <pre><code class="language-bash">.\windows\esputil -p COMPORT flash uart-bridge.hex</code></pre>|
+  | Linux   | <pre><code class="language-bash">./linux/esputil -p COMPORT flash uart-bridge.hex</pre> |
+  | MacOS   | <pre><code class="language-bash">./macos/esputil -p COMPORT flash uart-bridge.hex</code></pre> |
+
+Next step is to monitor and follow the instructions.
+
+```sh
+esputil -p COMPORT monitor
+```
+
+Note: if monitor command shows constant restarts, the flash parameters
+settings can be wrong. Reflash your device with `-fp ...` flash parameters
+settings. For example, WROOM-32 based boards use `-fp 0x220`:
+
+```sh
+esputil -p COMPORT -fp 0x220 flash uart-bridge.hex
+```
+
+For more on possible options for flash parameters, see
+https://github.com/cpq/esputil#flash-parameters