Langmuir.jl extension

[viniviena]

Hi!

As talking to Francesca, we discussed opportunities to create an extension to Mocca.jl using Langmuir.jl :).

I am open to discuss directions for opening a PR.

[FrancescaWatson]

Hi, Thanks for opening an issue!

Currently @jakobtorben is working through some steps to abstract out the isotherm interface to make it easier to connect new models. Shouldn't take too long. We will keep you posted!