Add enable_millisecond to duration selector (#34043)

source/_docs/blueprint/selectors.markdown

@@ -616,6 +616,11 @@ enable_day:
   type: boolean
   default: false
   required: false
+enable_millisecond:
+  description: When `true`, the duration selector will allow selecting milliseconds.
+  type: boolean
+  default: false
+  required: false  
 {% endconfiguration %}
 
 The output of this selector is a mapping of the time values the user selected.
@@ -626,6 +631,7 @@ days: 1 # Only when enable_day was set to true
 hours: 12
 minutes: 30
 seconds: 15
+milliseconds: 500 # Only when enable_millisecond was set to true
 ```
 
 ## Entity selector
@@ -1528,4 +1534,4 @@ The output of this selector is a list of triggers. For example:
 - platform: numeric_state
   entity_id: "sensor.outside_temperature"
   below: 20
-```
+```