Make it possible to configure Blackfroday per language

See #2309

content/content/multilingual.md

@@ -38,16 +38,22 @@ and taxonomy pages will be rendered below `/en` in English, and below `/fr` in F
 
 Only the obvious non-global options can be overridden per language. Examples of global options are `BaseURL`, `BuildDrafts`, etc.
 
-Taxonomies configuration can also be set per language, example:
+Taxonomies and Blackfriday configuration can also be set per language, example:
 
 ```
 [Taxonomies]
 tag = "tags"
 
+[blackfriday]
+angledQuotes = true
+hrefTargetBlank = true
+
 [Languages]
 [Languages.en]
 weight = 1
 title = "English"
+[Languages.en.blackfriday]
+angledQuotes = false
 
 [Languages.fr]
 weight = 2