Arduino Nano 33 BLE Sense Microphone does not appear in the list of external sensors

**Description**
The Arduino Science Journal Android application can retrieve data from the Arduino Nano 33 BLE Sense via BLE. The application does not list Nano Sense's microphone in the list of external sensors. All other sensors are available in the list (i.e. gesture, proximity, light color, light intensity, IMU, barometer)

**To Reproduce**
Steps to reproduce the behavior (Windows 10 Home, Version 21H1):
1. Connect the Arduino Nano 33 BLE sense to the computer.
2. Fire up the Arduino IDE (Version 1.8.15). Go to `File->Examples->Arduino_ScienceJournal->Nano33BLESenseFirmware`. Follow the instructions from [Arduino Science Journal website](https://science-journal.arduino.cc/sj/module/getting-started-2/lesson/external-sensors) to ensure you have to correct board platform and necessary libraries installed.
3. Once the `Nano33BLESenseFirmware` is uploaded onto the device, go to the Arduino Science Journal application. Under a new experiment, tap Sensors and then the gear button [as explained in this video](https://www.datocms-assets.com/32464/1615793894-sj11connectingamicrocontrollerv2oc.mp4).
4. Now, observe that in the list of external sensors (Sensors of Nano Sense board), the microphone is missing. Which means that a user can't retrieve sound data from the microcontroller via the application.

**Expected behavior**
Arduino Nano 33 BLE sense's microphone data cannot be retrieved from the Arduino science journal application.

**Desktop:**
- OS: Windows 10 Home, Version 21H1
- Browser: Firefox
- Arduino IDE Version: 1.8.15
- Board Platform: Arduino MBed OS, Version 1.3.2

**Smartphone:**
- Device: Samsung Galaxy M20
- OS: Android Version 10
- Browser: Firefox 89.1.1

Start with the Arduino IDE's File > Examples > Arduino_ScienceJournal > Nano33BLESenseFirmware entry point and the Android app's Sensors and external-sensor list described in the report. Trace how the Nano Sense sensors are exposed and mapped, then verify that microphone data appears in the list and can be retrieved.

Written by the indexing model from the issue text.