chore(docs): added duration example to the wing by example docs (#7215)

Closes #7103, added an example for `duration` with Wing.

docs/by-example/37-duration.md

@@ -0,0 +1,41 @@
+---
+title: Duration
+id: duration
+slug: /duration
+sidebar_label: Duration
+description: Get duration of time in Wing
+keywords: [Wing language, Type reflection]
+image: /img/wing-by-example.png
+custom_edit_url: https://github.com/winglang/wing/blob/main/docs/by-example/37-duration.md
+---
+
+The [duration](/docs/api/standard-library/std/duration) represents a length of time in Wing.
+
+You can use this to get durations representing the amount of milliseconds, seconds, minutes, hours, days, and years.
+
+```js playground example title="main.w"
+let msInHour = duration.fromHours(1).milliseconds;
+let msInSeconds = duration.fromSeconds(30).milliseconds;
+let secondsInDay = duration.fromDays(1).seconds;
+let hoursInDay = duration.fromDays(1).hours;
+let hoursInMonth = duration.fromMonths(1).hours;
+let daysInYear = duration.fromYears(1).days;
+
+let durations = {
+  msInHour,
+  msInSeconds,
+  secondsInDay,
+  hoursInDay,
+  hoursInMonth,
+  daysInYear
+};
+
+log(Json.stringify(durations));
+```
+
+```bash title="Wing console output"
+# Run locally with wing console
+{"msInHour":3600000,"msInSeconds":30000,"secondsInDay":86400,"hoursInDay":24,"hoursInMonth":730,"daysInYear":365}
+```
+
+