Consolidate materials related to JupyterHub

[leewujung]

Currently materials related to JupyterHub are presented in 2 places: Pre-event preparation and Tutorials/Getting Started which makes it confusing.

I think we can consolidate all JupyterHub-related materials to under Pre-event preparation and just add a link at the Tutorials section.

Pinging @emiliom and @ocefpaf -- not urgent.

[emiliom]

I don't have the bandwidth this week. Let's wait till next week, b/c I'm also adapting some of that same material for Waterhackweek, which started today.

I forget if I made that distinction or if I inherited it -- and liked it -- from ICESat-2 hackweek. It's there for a logical reason, though we could well argue that it's better to consolidate the materials. We can discuss next week.