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

dune-project

@@ -0,0 +1,24 @@
+(lang dune 3.20)
+
+(name remind_sync)
+
+(generate_opam_files true)
+
+(source
+ (uri https://git.donadeo.net/pdonadeo/remind-sync))
+
+(authors "Paolo Donadeo <paolo@donadeo.net>")
+
+(maintainers "Maintainer Name <maintainer@example.com>")
+
+(license MIT)
+
+(documentation https://git.donadeo.net/pdonadeo/remind-sync)
+
+(package
+ (name remind_sync)
+ (synopsis "A short synopsis")
+ (description "A longer description")
+ (depends ocaml)
+ (tags
+  ("add topics" "to describe" your project)))