I watching new packages of nimble directory in Slack. But I noticed that RSS feed has stopped.
I validated `packages.xml` with [Feed Validation Service](https://validator.w3.org/feed/). The result is below. [https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fnimble.directory%2Fpackages.xml](https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fnimble.directory%2Fpackages.xml) Error was found.
