Calculate hash on pass-through (#70)

packages/api-jsonrpc/src/chain/newHead.js

@@ -16,6 +16,7 @@ module.exports = ({
   isSubscription: true,
   inputs: [],
   output: {
-    type: 'Header'
+    type: 'Header',
+    withHash: true
   }
 }: InterfaceMethodDefinition);

packages/api-jsonrpc/src/types.js

@@ -16,7 +16,8 @@ export type InterfaceInputType = {
 };
 
 export type InterfaceOutputType = {
-  type: FormatOutputType
+  type: FormatOutputType,
+  withHash?: boolean
 };
 
 export type InterfaceMethodDefinition$Subscribe = {