Add warning to cone description

metadata/info.tangential.cone.yml

@@ -9,6 +9,9 @@ Changelog: https://github.com/bradyt/cone/blob/HEAD/cone_android/CHANGELOG.md
 
 AutoName: cone
 Description: |
+    Warning: the app occasionally does not save a transaction to file;
+    see https://github.com/bradyt/cone/issues/23
+
     Whereas ledger-cli is the original ledger app, and hledger, beancount
     and transity are a few of the number of ledger-likes, cone brings the
     data entry aspect to your mobile phone. We hope to add features to show