Only show rating button when user is eligible to rate

Summary:
Behind a gk.

This uses a hidden webview to check if a user is eligible for star ratings. This means you can practively ask the user, and makes sure you'll get an unbiased distribution.

Reviewed By: danielbuechele

Differential Revision: D17343118

fbshipit-source-id: fe7471416aef947ec10f4734e4136868ab5ab3e5

src/fb-stubs/UserFeedback.tsx

@@ -5,6 +5,8 @@
  * @format
  */
 
+import {Component} from 'react';
+
 export type FeedbackPrompt = {
   preSubmitHeading: string;
   postSubmitHeading: string;
@@ -28,3 +30,6 @@ export async function submitComment(
 export async function getPrompt(): Promise<FeedbackPrompt> {
   throw new Error('Method not implemented.');
 }
+export class StarRatingsEligibilityChecker extends Component<{
+  callback: (userIsEligible: boolean) => void;
+}> {}