docs: mark P15/P16 as unsupported and P17 as done; store original iCal event in rem

bin/remind.ml

@@ -31,6 +31,7 @@ type simple_monthly = {
 type rem = {
   source : string;  (** Source file or identifier for the reminder *)
   original_uuid : string;  (** Original UID from the iCalendar event *)
+  original_event : Icalendar.event option;  (** The original iCalendar event *)
   summary : string;  (** Summary or title of the reminder *)
   location : string option;  (** Optional location of the event *)
   description : string option;  (** Optional description of the event *)
@@ -56,6 +57,7 @@ let empty =
   {
     source = "";
     original_uuid = "";
+    original_event = None;
     summary = "";
     location = None;
     description = None;