Silence undefined type warnings for json-plist

Co-authored-By: Tom Gillespie <tgbugs@users.noreply.github.com>

Author: nnicandro

jupyter-base.el

@@ -39,6 +39,8 @@
 (declare-function jupyter-message-content "jupyter-messages" (msg))
 (declare-function jupyter-new-uuid "jupyter-messages")
 
+(cl-deftype json-plist () '(satisfies json-plist-p))
+
 ;;; Custom variables
 
 (defcustom jupyter-pop-up-frame nil