[mod] add 'Accept-Language' HTTP header to online processores

Most engines that support languages (and regions) use the Accept-Language from
the WEB browser to build a response that fits to the language (and region).

- add new engine option: send_accept_language_header

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

searx/engines/google_play_apps.py

@@ -22,6 +22,8 @@ about = {
 }
 
 categories = ["files", "apps"]
+send_accept_language_header = True
+
 search_url = "https://play.google.com/store/search?{query}&c=apps"