WIP: Retry link checking

[wolf99]

I saw another repo that similary uses lychee had some fails around the same time but since started working again.
Using this PR to check if the issue remains or is resolved in the lychee action.

[ryanplusplus]

I took a quick look and the failing links may actually be down

[wolf99]

@ryanplusplus looked like some temporary issue with gnu.org and drdobbs is actually gone.
Trying if some things for the the gnu.org errors for now

[wolf99]

Using the info here to help debug the issues: https://lychee.cli.rs/troubleshooting/network-errors/

Looks like the 403 from stackoverflow is due to that site using Cloudflare Bot Management.
Per: https://builtwith.com/detailed/stackoverflow.com.
So we may just have to ignore stackoverflow URLs :/

[wolf99]

Trying some of the suggestions at: https://lychee.cli.rs/troubleshooting/rate-limits/#_top

Looks like default concurrent network requests is 128.

[wolf99]

Still not sure if I'm using the correct token.
@ErikSchierboom do you know if there is a token with this name configured for Exercism? secrets.GITHUB_TOKEN

[ErikSchierboom]

${{ secrets.GITHUB_TOKEN }} is the right token