Add note to rule exception docs (#1977)

docs/detections/detections-ui-exceptions.asciidoc

@@ -8,11 +8,16 @@ processes and network activity to function without producing unnecessary noise.
 
 You can add multiple exceptions to one rule.
 
-IMPORTANT: When you add an exception to the
+[IMPORTANT]
+=====
+When you add an exception to the
 <<endpoint-rule-exceptions, Elastic Endpoint Security>> rule, you can select to
 add the exception to the Endpoint. When selected, the exception is added to
 both the detection rule *and* the Elastic Endpoint agent on your hosts.
 
+{ref}/binary.html[Binary fields] are not supported in detection rule exceptions.
+=====
+
 In addition to defining exception queries for source event values, you can use rule
 exceptions with value lists. Value lists are lists of items with
 the same {es} {ref}/mapping-types.html[data type]. You can create value lists