drop nodes when json file's timestamp is too old

[Djfe]

example: KBU has json files that haven't been updated in a year. (timestamp from may 2023)
We should not track/crawl those i.e. ignore them.

[AiyionPrime]

Maybe start with a github action, which warns about too old files?

[Djfe]

probably.
same goes for files that are not available anymore (404) or where the server doesn't respond, or where SSL errors.
I sorted out quite a few of those with #43 and #44