Add a cooling period

[TanyaS08]

For now we only 'proof' and 'bake' the landscape. It might be useful to also add a cooling period so that community dynamics can stabilise without having to deal with a changing environment.

This should be super easy and but it will be important to change the metacommunity that is called in the boundaries.jl script. Or rename them differently in the code.jl script

[tpoisot]

We can also simply do it by adding a bunch of timesteps from the metacommunity endpoint, and using the stable environment at the end of the baking period. Maybe we can wrap this into a function to do all three steps though.