Fix TODO to handle multi-line arguments

basic-concepts.scrbl

@@ -59,4 +59,5 @@ Because the @secref{images} that Apt provides boot on both virtual and physical
 machines, in most cases, switching means simply modifing one's profile to
 request the other type of resource.
 
-@TODO{This suggests we ought to make it easier at instantiation time to pick VMs or bare metal.}
+@TODO{This suggests we ought to make it easier at instantiation time to pick
+VMs or bare metal.}

defs.rkt

@@ -6,8 +6,8 @@
 (define (apturl page)
   (string-append "https://www.aptlab.net/" page))
 
-(define (TODO what)
-  (bold (string-append "TODO: " what)))
+(define (TODO . what)
+  (bold "TODO: " what))
 
 (define nodetype
   (lambda (typename howmany . properties)