Warn the user there if there were any conversion errors when converting the syntax to CommonMark Markdown Syntax 1.2 and choosing to convert the content automatically

When you ChangeSyntax  from XWiki 2.1 to CommonMark Markdown Syntax 1.2

• Choose Yes when asked to convert the page content and meta data from the previous XWiki 2.1 syntax to the selected CommonMark Markdown 1.2 syntax

The actual result (as documented)

• If you accept the Syntax conversion, by clicking "Yes", then XWiki will update the content with the result of the conversion. The quality of the conversion will usually be good, but may depend on the quality of the original Syntax. You need to review the quality of the conversion by checking for conversion errors that can appear.

However, while for some pages the result is quite good, for other pages some users may get confused if there were conversion errors. The page content is updated with the result of the conversion and when viewing the page it may look as broken ( e.g if there were styling, table formatting issues or other).

This could be improved by displaying an error message that some page content elements can't be properly converted or warn the user they need to check for the specific conversion errors (if possible to detect them beforehand).

Thanks!