[fix] brave engine: shows descriptions with their correct URLs

BTW add about section to the YAML configuration

It now shows descriptions with their correct URLs when there are videos in the
search results, pulling content_xpath from snippet-description instead of
snippet-content.

Suggested-by: @eagle-dogtooth https://github.com/searx/searx/issues/2857#issuecomment-869119968


Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>