add hydrate method that uses reactDOM.hydrate

Author: brucewpaul

packages/enzyme-adapter-react-16/src/ReactSixteenAdapter.js

@@ -175,6 +175,22 @@ class ReactSixteenAdapter extends EnzymeAdapter {
           instance.setChildProps(el.props, context, callback);
         }
       },
+      hydrate(el, context, callback) {
+        if (instance === null) {
+          const ReactWrapperComponent = createMountWrapper(el, options);
+          const wrappedEl = React.createElement(ReactWrapperComponent, {
+            Component: el.type,
+            props: el.props,
+            context,
+          });
+          instance = ReactDOM.hydrate(wrappedEl, domNode);
+          if (typeof callback === 'function') {
+            callback();
+          }
+        } else {
+          instance.setChildProps(el.props, context, callback);
+        }
+      },
       unmount() {
         ReactDOM.unmountComponentAtNode(domNode);
         instance = null;