Update C/C++ docs

Author: Thibaut

lib/docs/filters/cpp/entries.rb

@@ -31,6 +31,8 @@ def get_type
           'Keywords'
         elsif subpath.start_with?('experimental')
           'Experimental libraries'
+        elsif subpath.start_with?('language/')
+          'Language'
         elsif type = at_css('.t-navbar > div:nth-child(4) > :first-child').try(:content)
           type.strip!
           type.remove! ' library'