update docs

Author: adriangb

docs/source/user-guide/sql/aggregate_functions.md

@@ -66,6 +66,7 @@ Note: When no rows pass the filter, `COUNT` returns `0` while `SUM`/`AVG`/`MIN`/
 - [median](#median)
 - [min](#min)
 - [percentile_cont](#percentile_cont)
+- [quantile_cont](#quantile_cont)
 - [string_agg](#string_agg)
 - [sum](#sum)
 - [var](#var)
@@ -424,6 +425,14 @@ An alternate syntax is also supported:
 +---------------------------------------+
 ```
 
+#### Aliases
+
+- quantile_cont
+
+### `quantile_cont`
+
+_Alias of [percentile_cont](#percentile_cont)._
+
 ### `string_agg`
 
 Concatenates the values of string expressions and places separator values between them. If ordering is required, strings are concatenated in the specified order. This aggregation function can only mix DISTINCT and ORDER BY if the ordering expression is exactly the same as the first argument expression.