Add Stalebot configuration

Resolves #2602.

Author: marcphilipp

Diff for: .github/stale.yml

@@ -0,0 +1,69 @@
+# Configuration for probot-stale - https://github.com/probot/stale
+# Configuration options apply to both Issues and Pull Requests.
+# We configure those individually to match our workflow (see `pulls:` and `issues:`)
+
+pulls:
+  # Number of days of inactivity before a Pull Request becomes stale
+  daysUntilStale: 60
+
+  # Number of days of inactivity before a Pull Request with the stale label is closed.
+  # Set to false to disable. If disabled, Pull Request still need to be closed manually, but will remain marked as stale.
+  daysUntilClose: 21
+
+  # Comment to post when marking as stale. Set to `false` to disable
+  markComment: >
+    This pull request has been automatically marked as stale because it has not had recent activity.
+    Given the limited bandwidth of the team, it will be closed if no further activity occurs.
+    If you intend to work on this pull request, please reopen the PR.
+    Thank you for your contributions.
+  # Comment to post when closing a stale Pull Request.
+  closeComment: >
+    This pull request has been automatically closed due to inactivity.
+    If you are still interested in contributing this, please ensure that
+    it is rebased against the latest branch (usually `main`), all review
+    comments have been addressed and the build is passing.
+issues:
+  daysUntilStale: 365
+
+  # Number of days of inactivity before an Issue with the stale label is closed.
+  # Set to false to disable. If disabled, issues still need to be closed manually, but will remain marked as stale.
+  daysUntilClose: 21
+
+  # Comment to post when marking as stale. Set to `false` to disable
+  markComment: >
+    This issue has been automatically marked as stale because it has not had recent activity.
+    Given the limited bandwidth of the team, it will be automatically closed if no further
+    activity occurs.
+    Thank you for your contribution.
+  # Comment to post when closing a stale Issue.
+  closeComment: >
+    This issue has been automatically closed due to inactivity. If you have a good use case for this
+    feature, please feel free to reopen the issue.
+
+# Only issues or pull requests with all of these labels are check if stale. Defaults to `[]` (disabled)
+#onlyLabels: []
+
+# Issues or Pull Requests with these labels will never be considered stale. Set to `[]` to disable
+exemptLabels: []
+
+# Set to true to ignore issues in a project (defaults to false)
+exemptProjects: false
+
+# Set to true to ignore issues in a milestone (defaults to false)
+exemptMilestones: false
+
+# Set to true to ignore issues with an assignee (defaults to false)
+exemptAssignees: false
+
+# Label to use when marking as stale
+staleLabel: "status: stale"
+
+# Comment to post when removing the stale label.
+# unmarkComment: >
+#   Your comment here.
+
+# Limit the number of actions per hour, from 1-30. Default is 30
+limitPerRun: 30
+
+# Limit to only `issues` or `pulls`
+# only: issues