Fix .editorconfig settings for rc, JSON and YAML files

[raduserbanescu]

The EditorConfig documentation (§ file-format-details) states:

{s1,s2,s3}: Matches any of the strings given (separated by commas) (Available since EditorConfig Core 0.11.0)

The current setup does not work neither when editing nor when creating files (rc files, *.json, *.yml). It should be changed to:

 # Json, YAML and Configuration files
-[.*rc,*.{json,yml}]
+[{.*rc,*.{json,yml}}]
 indent_style = space
 indent_size = 2

With the fixed setup, the EditorConfig settings apply properly for rc files, *.json, *.yml. Tested with the Atom plug-in and by linting the whole project with the echint package.

Note: It does not work with the Sublime Text plug-in neither with the old nor with the updated setup.