DX-1846: Bump HTMLProofer from v3 to v4#298

asbjornu wants to merge 9 commits intomainSwedbankPay/jekyll-plantuml-docker:mainfrom

feature/dx-1846_htmlproofer_bumpSwedbankPay/jekyll-plantuml-docker:feature/dx-1846_htmlproofer_bumpCopy head branch name to clipboard