Support one bond defining another

[fonsp]

This currently works in Pluto, but not in PlutoSliderServer:

@bind x Slider(1:10)

@bind y Slider(1:x)

x, y

Why? When moving the y slider in normal Pluto, we just send the y value to the Pluto server, it sets it in the notebook process and runs the dependent cells (just cell 3). In PlutoSliderServer, moving y will send x and y together, this is our stateless idea.

Pluto does not handle this correctly (this is a bug in Pluto, not PSS): it first sets both x and y in the notebook process, and then runs the cells that depend on them: cells 2 and 3. The problem is: running cell 2 will set y to its initial value: 1, and you will always see x, 1 in the third cell.

I already have an example notebook for this: https://github.com/JuliaPluto/PlutoSliderServer.jl/blob/main/test/onedefinesanother.jl

[fonsp]

Fixed by fonsp/Pluto.jl#2014 , update Pluto to 0.19.5 or above to get this feature