[Feature] On/Off

[BlueAndi]

Is your feature request related to a problem? Please describe. N/A

Describe the solution you'd like Being able to switch Pixelix on and off, by

• user button
• REST API
• MQTT API

Describe alternatives you've considered N/A

Additional context want to happen. In off state:

• Light sleep mode.
• User button as wakeup source.
• WiFi is off.

Don't switch off during a running update.