Env variables need quotes, strings for everyone! (#16)

diff --git a/README.md b/README.md
index f0a32c6..0d1c08b 100644
--- a/README.md
+++ b/README.md
@@ -40,7 +40,7 @@
   secrets = ["GITHUB_TOKEN"]
 
   env = {
-    NO_BRANCH_DELETED_EXIT_CODE = 0
+    NO_BRANCH_DELETED_EXIT_CODE = "0"
   }
 }
 ```