Adding option for vertical brightness slider and custom brightness slider handle shape

[mcsheffrey]

I love this color picker! Great work making it easy to setup and customize.
I customized it a bit for my use case making the brightness slider vertical and changing the shape of the brightness slider handle.
Would you like me to make a PR to add these as customization options?

[shoaibnomani]

@mcsheffrey Hey! Can you please share how you managed to make this vertical? We want a similar solution for our app. Thanks!