[FEATURE]General volume control as a slider

Hello, Thank you so much for this Git.  I am new to all of this and have been working on programming my raspberry Pi with this.  I am learning through trial and error.  One thing I am uncertain, is it possible to add volume control to Homekit with this Git?

I would like to have a volume up and a volume down control.  I have implemented the general mute.

Thank you again.
