Adding lazyObjectsRuntime option to the Prepack Website

Summary:
This addresses the issue #1282 although the issue also requests for --additionalFunctions option which is not part of this commit. User should now be able to see --lazyObjectsRuntime option in the options list on https://prepack.io/repl.html. Ideally this should be an enum but this will accept a freeform string in this revision.
Closes #1475

Differential Revision: D7059756

Pulled By: phanipattapu

fbshipit-source-id: 588f688a52e81d065cf19ac1fbd358a9332b81a0

website/js/repl.js

@@ -44,6 +44,12 @@ var optionsConfig = [
     defaultVal: "browser",
     description: "The target environment for Prepack"
   },
+  {
+    type: "string",
+    name: "lazyObjectsRuntime",
+    defaultVal: "",
+    description: "Enable lazy objects feature and specify the JS runtime that supports this feature."
+  },
   {
     type: "boolean",
     name: "omitInvariants",