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/commandLine.ml

@@ -0,0 +1,17 @@
+open Cmdliner
+open Cmdliner.Term.Syntax
+
+let ical_file =
+  let doc = "TODO" in
+  let docv = "ICAL" in
+  Arg.(required & pos ~rev:true 0 (some string) None & info [] ~docv ~doc)
+
+let main_command f =
+  let doc = "Convert iCalendar files to remind format" in
+  let man = [] in
+  Cmd.make (Cmd.info "ical2rem" ~version:"%%VERSION%%" ~doc ~man)
+  @@
+  let+ ical_file = ical_file in
+  f ical_file
+
+let main f = Cmd.eval @@ main_command f