Add obsidian theme

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/user/configs/gui/obsidian/default.nix

@@ -52,6 +52,8 @@
           ./snippets/editor-monospace.css
           ./snippets/file-explorer-separators.css
         ];
+
+        theme = import ./themes/minimal.nix { inherit pkgs; };
       };
     };