fix(flow.ts): add importKind field to ImportSpecifier

Author: jedwards1211

def/flow.ts

@@ -404,6 +404,9 @@ export default function (fork: Fork) {
 
   def("ImportDeclaration")
     .field("importKind", or("value", "type", "typeof"), () => "value");
+  
+  def("ImportSpecifier")
+    .field("importKind", or("value", "type", "typeof"), defaults["null"]);
 
   def("FlowPredicate").bases("Flow");