feat: Org-roam

- Sets some basic keybinds.
- Sets up a temporary Syncthing config on the Nix end.
  - This ought to be replaced with a nicer system at some point.

modules/nixos/syncthing.nix

@@ -1,5 +1,7 @@
 { config, lib, pkgs, ... }:
 
+# TODO: This is a Deertopia module.  Move to nixos/deertopia/syncthing.nix.
+
 let cfg = config.sydnix.syncthing;
 in {
   options = {