Add a script to configure audio devices

[hello-amal]

Description

#62 and #64 added bi-directional audio capabilities to the web interface. However, this working is contingent on proper configuration of (possibly external) audio devices.

This PR adds README instructions for configuring audio devices, and adds a convenience bash script for configuring audio devices.

Testing procedure

• Have no external audio devices plugged in. Verify that the physical volume knob on the Stretch3's head is turned all the way up. Run ./configure_audio.sh and then launch the interface. Verify both robot-to-operator audio streaming and operator-to-robot TTS work.
• Plug in an external microphone. Run ./configure_audio.sh and then launch the interface. Verify that robot-to-operator audio streaming uses the new mic, and that operator-to-robot TTS works.
• Disconnect the above mic and plug in another external mic. Repeat the above test.

Before opening a pull request

From the top-level of this repository, run:

• pre-commit run --all-files

To merge

• Squash & Merge