Document each type of Space View

[abey79]

Currently, the docs on space views is spread out in multiple places. Specifically, the list of available space views is buried in the reference, and doesn't include specific help (e.g. the tensor space view is far from trivial to use).

Each space view should be:

• have a linkable documentation section
• proper documentation of their features
• screenshot
• link to a web-demo/rrd where such a view exists and can be interact with
• archetypes doc should mention what their preferred/default space view is and link to their doc
• stretch goal: code snippet to instantiate them
• more?

This ties into the in-viewer onboarding story in multiple ways:

Some of the content will be reused/imported/downloaded for display from within the viewer. And the rest might be linked to from that space view explorer thing in the prototype above ("Learn more" button).