Fix authors links in the landing page

[ntluong95]

In the landing page index.qmd, some authors have links to their GitHub, others to Linkedin.
In addition, we had a report of huge amount of traffic on the server from epirhandbook.com/en/www.linkedin.com/

It was redirected from index.html, so there must be something to be investigated with LinkedIn links
From @aspina7

Think it's a simple problem tbh, JavaScript likely backend used to open a new browser tab ... And because the links are not done properly it just endless loop of doom. So someone just needs to go through the bit where authors are listed and fix the urls