Org-roam major redesign

… adds this, with org-roam-buffer-toggle

Great; I figured that was coming.

Not sure when or how you want bug reports, @jethro, but are you aware of this?

Error in post-command-hook (magit-section-update-highlight): (wrong-type-argument (or eieio-object class) nil obj)

I get it when turning on org-roam-mode, though not consistently enough for me to have a sense of details beyond that ATM.