Add “duration” to glossary (#48208)

* feature: add duration in glossary

* fix: Changes according to style guide

* fix: Add missing full stop

content/en/docs/reference/glossary/duration.md

@@ -0,0 +1,14 @@
+---
+title: Duration
+id: duration
+date: 2024-10-05
+full_link:
+short_description: >
+  A time interval specified as a string in the format accepted by Go's [time.Duration](https://pkg.go.dev/time), allowing for flexible time specifications using various units like seconds, minutes, and hours.
+aka:
+tags:
+- fundamental
+---
+In Kubernetes APIs, a duration must be non-negative and is typically expressed with a suffix. 
+For example, `5s` for five seconds or `1m30s` for one minute and thirty seconds.
+