Add support for pump rpm configuration to mqtt interface

[kevincw01]

💥 Proposal

What feature you'd like to see

There is currently no method to change the RPM of the pump from the mqtt interface.

Motivation

Lack of an MQTT interface limits the ability to programmatically make changes outside of the web interface.

Pitch

An mqtt interface will allow me to change the pump RPM for use of the waterfall. This action requires a decrease in the pump RPM for my system and my automation is mechanized within nodered.

I've already inplemented this and am creating this issue in accordance with the PR guidance.