add an ics file exporter class

app/src/main/kotlin/com/simplemobiletools/calendar/helpers/IcsExporter.kt

@@ -0,0 +1,24 @@
+package com.simplemobiletools.calendar.helpers
+
+import android.content.Context
+import com.simplemobiletools.calendar.helpers.IcsExporter.ExportResult.*
+
+class IcsExporter {
+    enum class ExportResult {
+        EXPORT_FAIL, EXPORT_OK, EXPORT_PARTIAL
+    }
+
+    var eventsExported = 0
+    var eventsFailed = 0
+
+    fun exportEvents(context: Context, path: String): ExportResult {
+
+        return if (eventsExported == 0) {
+            EXPORT_FAIL
+        } else if (eventsFailed > 0) {
+            EXPORT_PARTIAL
+        } else {
+            EXPORT_OK
+        }
+    }
+}