[material_3_demo] Support for dynamic change of the `dynamicSchemeVariant` for a color scheme

[reza00farjam]

Please provide a way to switch between different DynamicSchemeVariant values for a color scheme in Material 3 Demo. It is a very important part of defining a color scheme alongside the brightness parameter.

[ericwindmill]

@jwill Do you have thoughts on this?

[jwill]

Circle back with me after Nov 1 (vacay). TLDR, it does relate to some ideas I have but I'm not working on anything till I'm back.

[reza00farjam]

Hi @jwill It is Nov 22, I forgot it myself till today but here is your circle back notification :D

I am also free to contribute this part myself with a little conversation on the acceptable design for it, if you are working on something else. Thanks.