Update README

Author: junichi11

README.md

@@ -12,7 +12,7 @@ This plugin provides support for GitHub Issue Tracker.
 - Search issues with issue number or keywords
 - Create a new label
 - Create a new milestone
-- Set a schedule for an issue
+- Add issues to schedule categories
 
 ## Usage
 
@@ -25,6 +25,10 @@ This plugin provides support for GitHub Issue Tracker.
 5. Click Connect button (If you can't connect a repository, please try to check input values)
 6. Click OK button
 
+### Schedules
+
+If an issue has a milestone and it has a due date, the issue is added to schedule category.
+
 ## Default queries
 
 1. Open