Add bottom margin to comment thread buttons, fixes...

Add bottom margin to comment thread buttons, fixes https://github.com/microsoft/vscode-pull-request-github/issues/886

src/vs/workbench/contrib/comments/browser/media/review.css

@@ -353,6 +353,7 @@
 	width: auto;
 	padding: 4px 10px;
 	margin-left: 5px;
+	margin-bottom: 5px;
 }
 
 .monaco-editor .review-widget .body .comment-form .monaco-text-button {