Handle rate limit exceeded merge error (#119)

Author: ReallyLiri

.gitignore

@@ -1,2 +1,3 @@
+.idea
 .env
 node_modules/

lib/merge.js

@@ -345,7 +345,8 @@ function checkMergeError(e) {
   const m = e ? e.message || "" : "";
   if (
     m.includes("review is required by reviewers with write access") ||
-    m.includes("reviews are required by reviewers with write access")
+    m.includes("reviews are required by reviewers with write access") ||
+    m.includes("API rate limit exceeded")
   ) {
     logger.info("Cannot merge PR:", m);
     return "failure";