after command for all domains

[Shulyaka]

Currently the code supports executing arbitrary commands after wake and asr commands.
It can be configured the following way:

pipelines:
  default:
    asr:
      name: faster-whisper.client
      after:
        command: |
          date +"%F %T,%3N after asr"
    wake:
      name: porcupine1
      after:
        command: |
          date +"%F %T,%3N after wake"

This PR adds support for the "after commands" for all other domains in a similar way.
They can be used for notification sounds, for flashing the led while rhasspy is listening, thinking, or speaking, also for logging or cleanup purposes where needed and other customization without the need to modify the code.

[Shulyaka]

It appears to be duplicate of #17 (but covers more domains though)