Implement OS notification using ux.notify

[AllanOricil]

Description

This feature would be done after this one is implemented.

obs: I can implement it if you find people who would want it. This is something I would want when I was working with sf projects, at least.

Every synchronous and long running command would have to be updated with

ux.notify("message");
// or
ux.notify("message",  { ...optional_props });

When:

• env variable SF_NOTIFY = true
• global flag --notify true

It is an opt-in feature.

Value it delivers:

• developers will no longer need to keep an eye every now and then while executing synchronous and long running commands.

Looking and feel