perf(webcal): Optimised the resolve process.

According to RFC-5545 Specification, the timezone is marked in the field
DTEND.

webcal/src/main/java/cn/org/codecrafters/webcal/WebCalendarEvent.java

@@ -272,7 +272,8 @@ public final class WebCalendarEvent extends WebCalendarNode {
                 Optional.ofNullable(duration)
                         .map((item) -> "DURATION:PT" + item.getSeconds() + "S\n").orElse("") +
                 Optional.ofNullable(end)
-                        .map((item) -> "DTEND:" + end.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME) + "\n").orElse("") +
+                        .map((item) -> "DTEND" + Optional.ofNullable(timezone).map(tz -> ";TZID=" + tz).orElse("") + ":" +
+                                end.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME) + "\n").orElse("") +
                 Optional.ofNullable(classification)
                         .map((item) -> "CLASS:" + item.getClassification() + "\n").orElse("") +
                 Optional.ofNullable(comment).map((item) -> "COMMENT:" + item + "\n").orElse("") +

webcal/src/test/java/cn/org/codecrafters/webcal/test/TestWebCalendar.java

@@ -46,7 +46,7 @@ public class TestWebCalendar {
                 .setClassification(Classification.PUBLIC)
                 .setStart(LocalDateTime.of(2023, 8, 6, 0, 0, 0))
                 .setEnd(LocalDateTime.of(2023, 8, 6, 8, 0, 0))
-                .setLocation("湖南省长沙市天心区碧云路60号")
+                .setLocation("Hong Kong University, Pokfulam, Central West, Hong Kong S.A.R")
                 .setUid(UUID.randomUUID().toString())
                 .setTimezone("Asia/Hong_Kong"));