path-only links don't work

[databus23]

When the feed contains links without scheme+host+port but just a path like /some/blog/post they can't be opened by clicking on the entry in the menubar.

The error is "There is no application set to open the URL /some/blog/post."

Seems like the url is taken as is but ideally the missing stuff should be inferred from the feed url.

[databus23]

Example feed (any github releases feed), e.g. https://github.com/getsentry/sentry/releases.atom