JS: Add classes with decorators to MkDef

Author: asgerf

javascript/ql/lib/semmle/javascript/ApiGraphs.qll

@@ -778,6 +778,8 @@ module API {
         nd = any(ExportDeclaration decl).getDirectSourceNode(_)
         or
         nd = any(MemberDeclaration m).getInit().flow()
+        or
+        nd = any(ClassDefinition cls | exists(cls.getADecorator())).flow()
       } or
       MkUse(DataFlow::Node nd) { nd instanceof DataFlow::SourceNode } or
       /** A use of a TypeScript type. */