CI to check for outdated links

[verytactical]

• Check if we link to an outdated GitHub repo (we consider a repo as outdated if it's default (master / main) branch has not been updated for 12 months or more), moved from https://linear.app/the-open-network/issue/OPS-60/audit-github-repositories-for-outdated-or-abandoned-documentation

[novusnota]

We have that CI, it's just that we need to switch it from "Warning" to "Stop the build" — and it's better to do so once we're clear with the structure. That is, right before the first public release.

That CI uses the following command: npx mint broken-links

[verytactical]

We've already switched "link-rot" CI on.