Add PulseAudio audio device

[nanoqsh]

It would be great if the library supported PulseAudio too, I propose to add this with my implementation.

It also needs a way to select the desired implementation. I think the simplest approach is to add a pulse feature that disables ALSA support and selects PulseAudio. The pulse would be a great default choice imho. So, there's also the option of adding an alsa feature instead.

[mrDIMAS]

Add a feature for PulseAudio, alsa should be the default backend because the current implementation that uses it is well tested. While this implementation is new and needs to be tested.

[nanoqsh]

I added pulse feature and also alsa feature to make the alsa-sys dependency optional. This is not necessary, but it's convenient for those who want to compile pulse only

[mrDIMAS]

The code looks good, however there's this error in the CI: error: unexpected cfg condition value: impl-default. Could you please fix it?

[nanoqsh]

The code looks good, however there's this error in the CI: error: unexpected cfg condition value: impl-default. Could you please fix it?

@mrDIMAS It's done

[mrDIMAS]

I've published 2.0.0 with your changes.