added accessibility props for touchables

Summary:
accessibilityLabels are missing in these touchable*.js files.
for #5322
ide This is not tested yet. I will update with test.
Closes https://github.com/facebook/react-native/pull/5346

Reviewed By: svcscm

Differential Revision: D2882061

Pulled By: gkassabli

fb-gh-sync-id: dff0ef373e5f5895027cb1cc08c8887a6ace8eee

Examples/UIExplorer/TextInputExample.ios.js

@@ -348,7 +348,13 @@ exports.examples = [
   {
     title: 'Auto-focus',
     render: function() {
-      return <TextInput autoFocus={true} style={styles.default} />;
+      return (
+        <TextInput
+          autoFocus={true}
+          style={styles.default}
+          accessibilityLabel="I am the accessibility label for text input"
+        />
+      );
     }
   },
   {