Provide instructions how to take Julia-Oscar Jupyter notebooks and run them locally

[fingolfin]

We need to improve the example page by giving instructions somewhere how one can download these notebooks and get them to run locally. That includes installing Oscar.jl (we already describe this), but also IJulia. Finally, how shall the user "load and run" that notebook.

Note that notebooks may have further requirements beyond Oscar and IJulia. Perhaps we can or should change https://github.com/oscar-system/OSCARBinder to have a Project.toml (or perhaps multiple, one for example: move the examples into a subdirs, with their own Project.toml. Perhaps even with a Manifest.toml; I don't know, figuring this out is part of the job).

@rfourquet we (the OSCAR PIs) thought that maybe you could work on that, given that you are Julia expert. I don't know if you know anything about IJulia; but in a sense, if you don't, that might make you even more perfect for this... ;-)

[fingolfin]

@rfourquet in the PI meeting, there was also an agreement that it is better to point people at the GitHub rendering of notebook rather than to Binder. But upon reviewing the links on the examples page, I am not 100% sure I understand our reasoning on this anymore: the motivation was that we prefer "dead" prerecorded notebooks over live ones, at least for now, because the experience with the "live" ones was that those have problems all the time (takes very long to start processing; has issues because the docker image is outdated; doesn't work as it worked on our own computer; etc.).

While I understand these concerns and agree with them, it seems to me that the current links to https://nbviewer.jupyter.org are (a) pointing to "non-live" versions of the notebooks anyway, and (b) are snappy. So maybe I am missing something? @micjoswig ?

(Of course at some point in the future, we'd want something live, at least I would want that, but the technology better be rock solid for that, and performant, and right now this simply is not a priority and we have to direct our limited resources carefully)

[rfourquet]

The "dead" version (what is linked to currently) is indeed very snappy and seems appropriate, more so for "general" users than the rendered version on github (which is also great, but by default users won't be interested in github, and there is already a github link for those interested).

And I agree that the live version is quite slow to launch; that said, before it fully comes live, it's possible to start reading the notebook. But currently, I get a "kernel not found error"... so yes this seems premature for having the live version as default.