docs: add maskAccessLogQuery filter to documentation

Signed-off-by: Aleksandr Ponimaskin <aleksandr.ponimaskin@zalando.de>

Author: ponimas

docs/reference/filters.md

@@ -2772,6 +2772,20 @@ unverifiedAuditLog()
 unverifiedAuditLog("azp")
 ```
 
+### maskAccessLogQuery
+
+Filter `maskAccessLogQuery` masks values of the provided query parameters in access logs by replacing them with hashes. It accepts query parameter keys as arguments.
+
+Examples:
+
+```
+maskAccessLogQuery("key_1")
+```
+
+```
+maskAccessLogQuery("key_1", "key_2")
+```
+
 ## Backend
 ### backendIsProxy