feat: initial implementation of iCalendar to Remind converter

- Add project scaffolding (dune, dune-project, opam, .ocamlformat)
- Implement basic parsing and handling of iCalendar events
- Add event predicates for common event types (all-day, timed,
  recurrence, exceptions)
- Add transformation logic to map iCalendar events to Remind format
  (stub implementation)
- Provide utilities for extracting event details and converting
  dates/times
- Set up executable entrypoint and command-line interface using Cmdliner
- Include Remind event type definitions and helpers

bin/dune

@@ -0,0 +1,13 @@
+(executable
+ (public_name remind_sync)
+ (name main)
+ (modules main commandLine remind eventTransformer eventPredicates utils)
+ (preprocess
+  (pps ppx_deriving.show))
+ (libraries
+  ;remind_sync
+  cmdliner
+  icalendar
+  timedesc-tzdb.full
+  timedesc-tzlocal.unix
+  timedesc))