[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>

searx/settings.yml

@@ -1575,6 +1575,16 @@ engines:
     timeout: 5.0
     disabled: True
 
+  - name: brave
+    shortcut: brave
+    engine: xpath
+    paging: false
+    search_url: https://search.brave.com/search?q={query}
+    url_xpath: //div[@class="snippet fdb"]/a/@href
+    title_xpath: //span[@class="snippet-title"]
+    content_xpath: //div[@class="snippet-content"]
+    categories: general
+
 # Doku engine lets you access to any Doku wiki instance:
 # A public one or a private/corporate one.
 #  - name : ubuntuwiki