[enh] add Brave-Search engine (XPath)

Add https://search.brave.com which was requested by @kaonashi696 [1].
This patch was suggested by @eagle-dogtooth [2].

[1] https://github.com/searx/searx/issues/2857
[2] https://github.com/searx/searx/issues/2857#issuecomment-867199241



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