Update Tumbling Window Trigger

Tumbling Window Trigger supports "Month" frequency

Author: chez-charlie

articles/data-factory/how-to-create-tumbling-window-trigger.md

@@ -99,7 +99,7 @@ The following table provides a high-level overview of the major JSON elements th
 |:--- |:--- |:--- |:--- |:--- |
 | **type** | The type of the trigger. The type is the fixed value "TumblingWindowTrigger". | String | "TumblingWindowTrigger" | Yes |
 | **runtimeState** | The current state of the trigger run time.<br/>**Note**: This element is \<readOnly>. | String | "Started," "Stopped," "Disabled" | Yes |
-| **frequency** | A string that represents the frequency unit (minutes or hours) at which the trigger recurs. If the **startTime** date values are more granular than the **frequency** value, the **startTime** dates are considered when the window boundaries are computed. For example, if the **frequency** value is hourly and the **startTime** value is 2017-09-01T10:10:10Z, the first window is (2017-09-01T10:10:10Z, 2017-09-01T11:10:10Z). | String | "minute," "hour"  | Yes |
+| **frequency** | A string that represents the frequency unit (minutes, hours, or months) at which the trigger recurs. If the **startTime** date values are more granular than the **frequency** value, the **startTime** dates are considered when the window boundaries are computed. For example, if the **frequency** value is hourly and the **startTime** value is 2017-09-01T10:10:10Z, the first window is (2017-09-01T10:10:10Z, 2017-09-01T11:10:10Z). | String | "Minute," "Hour", "Month"  | Yes |
 | **interval** | A positive integer that denotes the interval for the **frequency** value, which determines how often the trigger runs. For example, if the **interval** is 3 and the **frequency** is "hour," the trigger recurs every 3 hours. <br/>**Note**: The minimum window interval is 5 minutes. | Integer | A positive integer. | Yes |
 | **startTime**| The first occurrence, which can be in the past. The first trigger interval is (**startTime**, **startTime** + **interval**). | DateTime | A DateTime value. | Yes |
 | **endTime**| The last occurrence, which can be in the past. | DateTime | A DateTime value. | Yes |