add doc on skip_render

Author: refraction-ray

src/maintainer/conda_forge_yml.rst

@@ -29,6 +29,7 @@ Top-level fields
 * osx
 * provider
 * recipe_dir
+* skip_render
 * templates
 * travis
 * win
@@ -273,6 +274,19 @@ The relative path to the recipe directory. The default is:
 
     recipe_dir: recipe
 
+skip_render
+---------
+This option specifies a list of files which conda smithy will skip rendering. 
+The possible values can be a subset of ``.gitignore``, ``.gitattributes``, ``README.md``, ``LICENSE.txt``.
+The default value is an empty list [ ], i.e. all these four files will be generated by conda smithy. 
+For example, if you want to customize .gitignore and LICENSE.txt file by your own, you shoud have the following configuration.
+
+.. code-block:: yaml
+    
+    skip_render:
+      - .gitignore
+      - LICENSE.txt 
+
 templates
 ---------
 This is mostly an internal field for specifying where templates files live.