make search language handling less strict

languages.py can change, so users may query on a language that is not
on the list anymore, even if it is still recognized by a few engines.

also made no and nb the same because they seem to return the same,
though most engines will only support one or the other.

searx/engines/bing.py

@@ -94,6 +94,8 @@ def _fetch_supported_languages(resp):
     options = dom.xpath('//div[@id="limit-languages"]//input')
     for option in options:
         code = option.xpath('./@id')[0].replace('_', '-')
+        if code == 'nb':
+            code = 'no'
         supported_languages.append(code)
 
     return supported_languages