Make it possible to configure Blackfroday per language

See #2309

helpers/configProvider.go

@@ -0,0 +1,25 @@
+// Copyright 2016-present The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package helpers implements general utility functions that work with
+// and on content.  The helper functions defined here lay down the
+// foundation of how Hugo works with files and filepaths, and perform
+// string operations on content.
+package helpers
+
+// ConfigProvider provides the configuration settings for Hugo.
+type ConfigProvider interface {
+	GetString(key string) string
+	GetStringMap(key string) map[string]interface{}
+	GetStringMapString(key string) map[string]string
+}