support notion site

### Category Blog ### Website URL https://notion.notion.site/ ### Website description support notion site https://<username>.notion.site/ like https://notion.notion.site/ ### What content should be included? iterate through links on that page and add articles. ### Additional description _No response_ ### This is not a duplicated rss request - [x] I have searched [existing issues](https://github.com/DIYgod/RSSHub/issues) and [pull requests](https://github.com/DIYgod/RSSHub/pulls) to ensure this rss proposal has not already been requested