[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/wikipedia.py

@@ -19,6 +19,9 @@ about = {
     "results": 'JSON',
 }
 
+
+send_accept_language_header = True
+
 # search-url
 search_url = 'https://{language}.wikipedia.org/api/rest_v1/page/summary/{title}'
 supported_languages_url = 'https://meta.wikimedia.org/wiki/List_of_Wikipedias'
@@ -41,9 +44,6 @@ def request(query, params):
     language = url_lang(params['language'])
     params['url'] = search_url.format(title=quote(query), language=language)
 
-    if params['language'].lower() in language_variants.get(language, []):
-        params['headers']['Accept-Language'] = params['language'].lower()
-
     params['headers']['User-Agent'] = searx_useragent()
     params['raise_for_httperror'] = False
     params['soft_max_redirects'] = 2