Add JSON filter to octocatalog-diff documentation

Author: Kevin Paulisse

doc/advanced-filter.md

@@ -10,6 +10,7 @@ Please note that there are other options to ignore specified diffs, including:
 Here is the list of available filters and an explanation of each:
 
 - [Absent File](/doc/advanced-filter.md#absent-file) - Ignore parameter changes of a file that is declared to be absent
+- [JSON](/doc/advanced-filter.md#json) - Ignore whitespace differences if JSON parses to the same object
 - [YAML](/doc/advanced-filter.md#yaml) - Ignore whitespace/comment differences if YAML parses to the same object
 
 ## Absent File
@@ -69,6 +70,20 @@ Wouldn't it be nice if the meaningless information didn't appear, and all you sa
       + absent
 ```
 
+## JSON
+
+#### Usage
+
+```
+--filters JSON
+```
+
+#### Description
+
+If a file resource has extension `.json` and a difference in its content is observed, JSON objects are constructed from the previous and new values. If these JSON objects are identical, the difference is ignored.
+
+This allows you to ignore changes in whitespace, comments, etc., that are not meaningful to a machine parsing the file. Note that changes to files may still trigger Puppet to restart services even though these changes are not displayed in the octocatalog-diff output.
+
 ## YAML
 
 #### Usage
@@ -81,4 +96,4 @@ Wouldn't it be nice if the meaningless information didn't appear, and all you sa
 
 If a file resource has extension `.yml` or `.yaml` and a difference in its content is observed, YAML objects are constructed from the previous and new values. If these YAML objects are identical, the difference is ignored.
 
-This allows you to ignore changes in whitespace, comments, etc., that are not meaningful to a machine parsing the file. Please note that by filtering these changes, you are ignoring changes to comments, which may be meaningful to humans.
+This allows you to ignore changes in whitespace, comments, etc., that are not meaningful to a machine parsing the file. Please note that by filtering these changes, you are ignoring changes to comments, which may be meaningful to humans. Also, changes to files may still trigger Puppet to restart services even though these changes are not displayed in the octocatalog-diff output.