implement visit duration

src/app/(main)/websites/[websiteId]/sessions/[sessionId]/SessionStats.tsx

@@ -1,6 +1,7 @@
 import { useMessages } from 'components/hooks';
 import MetricCard from 'components/metrics/MetricCard';
 import MetricsBar from 'components/metrics/MetricsBar';
+import { formatShortTime } from 'lib/format';
 
 export function SessionStats({ data }) {
   const { formatMessage, labels } = useMessages();
@@ -10,6 +11,11 @@ export function SessionStats({ data }) {
       <MetricCard label={formatMessage(labels.visits)} value={data?.visits} />
       <MetricCard label={formatMessage(labels.views)} value={data?.views} />
       <MetricCard label={formatMessage(labels.events)} value={data?.events} />
+      <MetricCard
+        label={formatMessage(labels.visitDuration)}
+        value={data?.totaltime / data?.visits}
+        formatValue={n => `${+n < 0 ? '-' : ''}${formatShortTime(Math.abs(~~n), ['m', 's'], ' ')}`}
+      />
     </MetricsBar>
   );
 }