Create button to download pluto/jupyter notebook of tutorial

@tmigot said
> I used this option generating the markdown and the Jupyter notebook in DCISolver: [juliasmoothoptimizers.github.io/DCISolver.jl/dev/example](https://juliasmoothoptimizers.github.io/DCISolver.jl/dev/example/)
What do you think of this solution?

> This tutorial might migrate here actually :).

@abelsiqueira said
> That's a good idea. I personally don't like Binder because it's too slow, but Julia really doesn't have anything for running code online :/
I clicked and it didn't have a Julia kernel, only Python3 - I think it was mentioned in the JOSS review already.

I'm counting on the tutorial migrating here soon :)

@tmigot said
> On the painful side, if the notebooks are in the gh-pages branch, the environment to run the binder needs to be at the source of this branch, which makes things very tricky I found