Add more 'age' input examples

Author: thisismydesign

README.md

@@ -42,7 +42,7 @@ jobs:
     - name: Remove old artifacts
       uses: c-hive/gha-remove-artifacts@v1
       with:
-        age: '1 month'
+        age: '1 month' # '<number> <unit>', e.g. 5 days, 2 years, 90 seconds, parsed by Moment.js
         # Optional inputs
         # skip-tags: true
         # skip-recent: 5