[chronik.e.cash] warn on broken links during docusaurus build

Summary:
Broken link errors are causing this build to fail in CI

The links are not actually broken. I am not sure why they are being detected as such. We have this same problem with the markdown linter, which is why arclint is ignoring this repo.

It's an issue that should be resolved (if practical) -- at the moment tho, looking to fix the broader npm module problem.

Test Plan:

docker build -f chronik.e.cash.Dockerfile -t chronik-docs .

builds

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16720