RSS Atom generated rss.xml are missing the required attribute.

[mrepol742]

Description

RSS sitemap can be read, but has errors

Error: Missing XML attribute

Steps to Reproduce

1. npm i
2. export NODE_OPTIONS=--openssl-legacy-provider && npm run build-git
3. Go to https://search.google.com/search-console/sitemaps and submit the file url
4. It'll show RSS sitemap can be read, but has errors

Your Environment

Description	Value
vuepress-plugin-feed version	0.1.9
node version	20.11.1
npm version	10.2.4
browser	Google Chrome Version 123.0.6312.58 (Official Build) (64-bit)
OS	Arch Linux x86_64

[webmasterish]

Thanks for reporting.

Unfortunately I don't have any free time at the moment to go through it, please feel free to submit a pull request.