add a word about PIPELINE_MIMETYPES

docs/configuration.rst

@@ -170,11 +170,27 @@ Other settings
 ``PIPELINE_TEMPLATE_SEPARATOR``
 ...............................
 
-  Charater chain used by Pipeline as replacement for directory separator.
+  Character chain used by Pipeline as replacement for directory separator.
 
   Defaults to ``"_"``
 
 
+``PIPELINE_MYMETYPES``
+......................
+
+  Tuple that match file extension with their corresponding mimetypes.
+
+  Defaults to ::
+  
+    (
+      (b'text/coffeescript', '.coffee'),
+      (b'text/less', '.less'),
+      (b'application/javascript', '.js'),
+      (b'text/x-sass', '.sass'),
+      (b'text/x-scss', '.scss')
+    )
+
+
 Embedding fonts and images
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