Allow strings in date range aggregation

Author: pquentin

specification/_types/aggregations/bucket.ts

@@ -695,15 +695,15 @@ export class AggregationRange {
   /**
    * Start of the range (inclusive).
    */
-  from?: double | null
+  from?: FieldValue
   /**
    * Custom key to return the range with.
    */
   key?: string
   /**
    * End of the range (exclusive).
    */
-  to?: double | null
+  to?: FieldValue
 }
 
 /**