Minor Description
Despite the fact that the placeholder displays an example of how a link to an external page should look, any user can mistakenly enter any character at the beginning in the value itself or at the end of it.
As a result, after saving such a link, the user will not be able to open the external page since the URL is not valid.
Therefore, either pre-saving or in real-time, XWiki should check whether the external link is valid (it URL syntax).
I am attaching the image that the user has when trying to open the link.
`https://extensions.xwiki.org/xwiki/bin/view/Extension/WikiLinkURLNormalizer/
