add context about updated_at support

this pr adds what type the updated_at field of the timestamp strategy should have in relation to iso date strings and unix epoch integers.

Resolves # #1948

website/docs/reference/resource-configs/updated_at.md

@@ -64,7 +64,7 @@ You will get a warning if the data type of the `updated_at` column does not matc
 ## Description
 A column within the results of your snapshot query that represents when the record row was last updated.
 
-This parameter is **required if using the `timestamp` [strategy](/reference/resource-configs/strategy)**.
+This parameter is **required if using the `timestamp` [strategy](/reference/resource-configs/strategy)**. The `updated_at` field may support ISO date strings and unix epoch integers, depending on the data platform you use. 
 
 
 ## Default