add io file

src/io.rs

@@ -0,0 +1,13 @@
+use ics::ICalendar;
+
+pub fn export(
+    timetable: Vec<crate::timetable::models::Day>,
+    dates: std::collections::HashMap<
+        usize,
+        Vec<(chrono::DateTime<chrono::Utc>, chrono::DateTime<chrono::Utc>)>,
+    >,
+) -> ICalendar<'static> {
+    let mut calendar = ICalendar::new("2.0", "cal8tor");
+
+    calendar
+}