Add support for audible notifications in Linux and WSL.

[zee-bit]

This issue is drawn-out from #887.

Currently, ZT supports audible notification only in OSX. We need to extend the support for other platforms as well. From a brief recent discussion in #development help, we are thinking of using a system package(like paplay from pulseaudio-utils) that should be included in most UNIX-based systems, so that we don't end up with another dependency(as with desktop notifications).

We should also ensure that we already have a robust fall-back in place, for some systems that are missing the above package. One approach as suggested in the above discussion is to use terminal-bell, though we are open to other methods for this.

Finally, this should all be wrapped up as an option on a per-stream basis too as requested in #887.

[zulipbot]

Hello @zulip/server-notifications members, this issue was labeled with the "area: notifications" label, so you may want to check it out!

[neiljp]

One related feature for this is to use the infrastructure provided by the server, as discussed at #backend > notification sounds

[neiljp]

Just to note here, that part of this work could involve packaging the default zulip notification sound and using that.

A good extension would then be the additional packaging of multiple sounds and allowing a choice to apply for terminal.