[Feature request] using Clifford algebra without using its type tree

[GiggleLiu]

e.g. Define Clifford algebra as macros like

@CliffordSet begin
    @PauliX XGate
    @PauliY XGate
    @PauliZ XGate
    ...
end

where XGate is some user defined types, and @Paulix maps it to the behavior of PauliX gate.

So that user can use arithmatics without using the type tree in Cliffords.jl?

This feature can make Cliffords.jl more useful, since to some project like our Yao.jl, it is hard to use type tree in Cliffords.jl directly.