Add note to further file

Author: Felicity Chapman

cpp/ql/src/jsf/4.20 Unions and Bit Fields/AV Rule 154.qhelp

@@ -5,6 +5,10 @@
 
 
 <overview>
+
+<!-- Mention that this rule may not be applicable in projects that don't follow the JSF standard. -->
+<include src="cpp/jsfNote.qhelp" />
+
 <p>
 This rule finds bit fields with members that are not explicitly declared to be unsigned.
 The sign of plain char, short, int, or long bit field is implementation-specific, and declaring