add request reviewers as attribute of GHPullRequest

Author: XericWei

src/main/java/org/kohsuke/github/GHPullRequest.java

@@ -58,6 +58,9 @@ public class GHPullRequest extends GHIssue {
     private int changed_files;
     private String merge_commit_sha;
 
+    // pull request reviewers
+    private GHUser[] requested_reviewers;
+
     /**
      * GitHub doesn't return some properties of {@link GHIssue} when requesting the GET on the 'pulls' API
      * route as opposed to 'issues' API route. This flag remembers whether we made the GET call on the 'issues' route
@@ -76,6 +79,7 @@ GHPullRequest wrapUp(GitHub root) {
         if (base != null) base.wrapUp(root);
         if (head != null) head.wrapUp(root);
         if (merged_by != null) merged_by.wrapUp(root);
+        if (requested_reviewers != null) GHUser.wrap(requested_reviewers, root);
         return this;
     }
 
@@ -219,6 +223,11 @@ public String getMergeCommitSha() throws IOException {
         return merge_commit_sha;
     }
 
+    public GHUser[] getRequestedReviewers() throws IOException {
+        populate();
+        return requested_reviewers;
+    }
+
     /**
      * Fully populate the data by retrieving missing data.
      *