Add org to front matter formats

actually it's 5, there's also csv. Afaict it's not meant to be used in that way
though so let's just add org.

docs/content/en/content-management/front-matter.md

@@ -23,7 +23,7 @@ toc: true
 
 ## Front Matter Formats
 
-Hugo supports three formats for front matter, each with their own identifying tokens.
+Hugo supports four formats for front matter, each with their own identifying tokens.
 
 TOML
 : identified by opening and closing `+++`.
@@ -34,6 +34,10 @@ YAML
 JSON
 : a single JSON object surrounded by '`{`' and '`}`', followed by a new line.
 
+ORG
+: a group of Org mode keywords in the format '`#+KEY: VALUE`'. Any line that does not start with `#+` ends the front matter section.
+  Keyword values can be either strings (`#+KEY: VALUE`) or a whitespace separated list of strings (`#+KEY[]: VALUE_1 VALUE_2`).
+
 ### Example
 
 {{< code-toggle >}}