These are still to be updated (as noted in the files), but it needs
doing before any kind of preliminary release. Plan is to refresh the
tutorial and make sure samples work again, then write a more
comprehensive document explaining changes since Idris 1.
This is an initial copy and refinement of the existing documentation for packaging.
This commit also starts the Idris2 reference documentation, in which we can start documenting the language proper. Maybe we should include the contents of `Notes` here, but that is a question for later.
