Audio guide in readme is outdated

[krns]

Environment

• Elixir version (elixir -v): 1.16.2
• Nerves environment: (mix nerves.env --info) dev
• Additional information about your host, target hardware or environment that
  may help

Current behavior

The readme says:

Audio

The Raspberry Pi has many options for audio output. This system supports the
HDMI and stereo audio jack output. The Linux ALSA drivers are used for audio
output.

The general Raspberry Pi audio documentation mostly applies to Nerves. For
example, to force audio out the HDMI port, run:

cmd("amixer cset numid=3 2")

Change the last argument to amixer to 1 to output to the stereo output jack.

This is no longer true since May 2020: https://www.raspberrypi.com/news/latest-raspberry-pi-os-update-may-2020/ (see "Other changes").

Some people have asked how they can switch the audio output from the command line without using the desktop. To do this, you will need to create a file called .asoundrc in your home directory; ALSA looks for this file to determine which audio device it should use by default. If the file does not exist, ALSA uses “card 0” – which is HDMI – as the output device.

Expected behavior

I would expect the readme to take this change into account :)

[fhunleth]

@krns Thanks for catching this. Could you make a PR that updates the text?

[krns]

@fhunleth I'd like to contribute, but I'm not sure what all is needed after the changes.

Do we already need an .asoundrc in the home directory for this? Do you already know more about it? Otherwise, I will try to delve deeper towards the end of the week.

[fhunleth]

That's fine. Support everything is really hard and filing this issue might get others involved.

I don't have a much experience with audio. I would expect that there's no need for a .asoundrc file, though, and that every option that would be put in the file could also be passed via the commandline. Passing everything via commandline args would keep all configuration in one place (in theory).

If you feel like you're not making any progress, one PR could be just to remove the wrong info from the README and point people to this issue for updates.