Configure stale and support Probots

.github/stale.yml

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+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 60
+# Number of days of inactivity before a stale issue is closed
+daysUntilClose: 7
+# Issues with these labels will never be considered stale
+exemptLabels:
+  - pinned
+  - security
+# Label to use when marking an issue as stale
+staleLabel: stale
+# Comment to post when marking an issue as stale. Set to `false` to disable
+markComment: >
+  This issue has been automatically marked as stale because it has not had
+  recent activity. It will be closed if no further activity occurs.
+
+  If this is still an issue for you, please try to help by debugging it
+  further and sharing your results.
+
+  Thank you for your contributions.
+
+# Comment to post when closing a stale issue. Set to `false` to disable
+closeComment: false

.github/support.yml

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+# Label used to mark issues as support requests
+supportLabel: question
+# Comment to post on issues marked as support requests. Add a link
+# to a support page, or set to `false` to disable
+supportComment: >
+  This looks like a support question. Please ask your support questions on
+  [StackOverflow](http://stackoverflow.com/questions/tagged/phpspreadsheet),
+  or [Gitter](https://gitter.im/PHPOffice/PhpSpreadsheet).
+
+  Thank you for your contributions.
+
+# Whether to close issues marked as support requests
+close: true
+# Whether to lock issues marked as support requests
+lock: false