Add links to open notebooks on a local Basthon notebook

[Naereen]

See a link like this:
https://besson.link/Basthon/notebook/?from=../../publis/notebooks/Py_Pi_Day_2017.ipynb
It works!

For most of my notebooks, using Basthon won't work because:

• I'm using other kernel than IPython: OCaml, C, Java, Rust, Julia, Bash, GNUPlot and even Octave!
• I'm using IPython magic a lot, like %timeit etc, which are not (yet) supported in Basthon (see https://framagit.org/casatir/basthon-kernel/-/issues/10).
• I'm using Jupyter notebook extensions, like itikz, lolviz, rcviz, watermark, cython, ipythonblocks, ipywidgets, etc.

But for the "pure Python" notebooks (even using numpy, matplotlib etc), I can use my locally available Basthon notebook (http://notebook.besson.link/ or https://besson.link/Basthon/notebook/) to load a notebook available from the same site.