fix(options)!: Default to 'Close as not planned'

GitHub introduced an additional close reason 'Close as not planned':
https://github.blog/changelog/2022-05-19-the-new-github-issues-may-19th-update/

'stale' is a use case for this close reason

Fixes #789

BREAKING CHANGE:
`close-issue-reason` defaults to `not_planned` (previously: ``
which defaulted to `completed`)
This closes the issue as 'not planned' on GitHub rather than 'completed'

See: https://github.blog/changelog/2022-05-19-the-new-github-issues-may-19th-update

README.md

@@ -44,7 +44,7 @@ Every argument is optional.
 | [close-pr-message](#close-pr-message)                               | Comment on the staled PRs while closed                                      |                       |
 | [stale-issue-label](#stale-issue-label)                             | Label to apply on staled issues                                             | `Stale`               |
 | [close-issue-label](#close-issue-label)                             | Label to apply on closed issues                                             |                       |
-| [close-issue-reason](#close-issue-reason)                           | Reason to use when closing issues                                           |                       |
+| [close-issue-reason](#close-issue-reason)                           | Reason to use when closing issues                                           | `not_planned`         |
 | [stale-pr-label](#stale-pr-label)                                   | Label to apply on staled PRs                                                | `Stale`               |
 | [close-pr-label](#close-pr-label)                                   | Label to apply on closed PRs                                                |                       |
 | [exempt-issue-labels](#exempt-issue-labels)                         | Labels on issues exempted from stale                                        |                       |
@@ -226,7 +226,7 @@ Required Permission: `issues: write`
 
 Specify the [reason](https://github.blog/changelog/2022-05-19-the-new-github-issues-may-19th-update/) used when closing issues. Valid values are `completed` and `not_planned`.
 
-Default value: unset
+Default value: `not_planned`
 
 #### stale-pr-label
 

__tests__/constants/default-processor-options.ts

@@ -53,6 +53,6 @@ export const DefaultProcessorOptions: IIssuesProcessorOptions = Object.freeze({
   ignoreIssueUpdates: undefined,
   ignorePrUpdates: undefined,
   exemptDraftPr: false,
-  closeIssueReason: '',
+  closeIssueReason: 'not_planned',
   includeOnlyAssigned: false
 });

action.yml

@@ -51,7 +51,7 @@ inputs:
     required: false
   close-issue-reason:
     description: 'The reason to use when closing an issue.'
-    default: ''
+    default: 'not_planned'
     required: false
   stale-pr-label:
     description: 'The label to apply when a pull request is stale.'