new buildSchedule function and tests for string parsing

src/commonMain/kotlin/com/insanusmokrassar/krontab/StringParser.kt

@@ -50,4 +50,9 @@ fun createSimpleScheduler(incoming: String): KronScheduler {
     return createKronScheduler(
         secondsParsed, minutesParsed, hoursParsed, dayOfMonthParsed, monthParsed
     )
-}
+}
+
+/**
+ *
+ */
+fun buildSchedule(incoming: String): KronScheduler = createSimpleScheduler(incoming)