[hugo] Check for broken internal links (maybe external)

[NissesSenap]

As in all documentation you start to have a bunch of links.
But sometimes you screw up or move a file and then all of the sudden you get broken links.

Hugo sadly don't have any built in tool to verify that all links that it creates is working.
I think the internal links is most important since we have most control around them.

If an external link breaks, so be it. It's something that we can fix when someone notices it.

[NissesSenap]

There where a few broken links fixed in: #954

[github-actions]

This issue hasn't been updated for a while, marking as stale, please respond within the next 7 days to remove this label

[NissesSenap]

This feature has been implemented, but we should fix the existing broken links and create a cronjob to run so we can see if this happens.