(doc) Document the new set-due-date option

Author: gep13

docs/input/docs/configuration/default-configuration.md

@@ -29,6 +29,7 @@ export:
  multiline-regex: false
 close:
  use-issue-comments: false
+ set-due-date: false
  issue-comment: |-
  :tada: This issue has been resolved in version {milestone} :tada:
 
@@ -186,6 +187,12 @@ tokenized values, such as milestone, owner, repository, with the actual values.
  - This is a template for what comment should be added to each issue. Within
  this comment template, it is possible to replace information for example,
  the milestone name, the owner/repository information, etc.
+- **set-due-date**
+ - A boolean value which indicates whether or not to set the due date of the
+ milestone when closing it. The date which it is set to, is the same as the
+ date at which the command was run, it is not possible to provide a
+ different date. **NOTE:** This configuration option was added in version
+ 0.19.0 of GitReleaseManager.
 
 ## Default branch