A52 documentation in need of updates.

[GitHub issues - opened]

alsa-project/alsa-plugins issue #29 was opened from quequotion:

[a52.txt](https://github.com/alsa-project/alsa-plugins/blob/4219f4b3fded74d7b07a54c3ba8661d7a18c3b6c/doc/a52.txt) hasn't been changed in fifteen years.

In that time, [a preconfiguration has been supplied that ends up getting merged into a dysfunctional mess if users add a manual configuration to their asound.conf without prepending an exclamation point to override it](https://github.com/alsa-project/alsa-lib/issues/154#issuecomment-859799234), and more recently [more sample formats have been added](https://github.com/alsa-project/alsa-plugins/commit/f11e7a8994111f971bc881d4069f768472452f4f).

This file needs some attention.

Issue URL     : https://github.com/alsa-project/alsa-plugins/issues/29
Repository URL: https://github.com/alsa-project/alsa-plugins