Regular validation of URLs in the catalog

[Vampire]

Description of the feature / enhancement.

It might be a good idea to have some scheduled action that regularly checks all URLs in the catalog for whether they are reachable and also deliver a valid parseable JSON Schema file.

Some URLs got outdated because branch names were changed.
Some URLs got outdated as their content is simply not available anymore.
Some URLs are plainly wrong like being the HTML view on GitHub, not the raw file.
Even a json.schemastore.org URL is wrong due to a missing character in the file name.
Currently 69 URLs did not pass a quick CLI check using HTTPie and jq.

Are you making a PR for this?

No, someone else must create the PR.