feat(workflow): add stalesweeper (#510)

.github/DISCUSSION_TEMPLATE/actions.yml

@@ -1,6 +1,6 @@
 ---
 title: "<Your question or feedback about our GitHub actions>"
-labels: [actions]
+labels: [Actions]
 body:
   - type: markdown
     attributes:

.github/workflows/discussions-stale.yml

@@ -0,0 +1,39 @@
+---
+name: Close Stale Discussions
+
+on:
+  schedule:
+    - cron: '00 11 * * *'
+  workflow_dispatch:
+    inputs:
+      dry-run:
+        description: 'Run the action without closing any discussions'
+        type: boolean
+
+jobs:
+  close-stale-discussions:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        category:
+          - 'Actions'
+          - 'GSMS'
+          - 'Sunshine'
+          - 'Themerr'
+    steps:
+      - name: stalesweeper
+        uses: steffen-karlsson/stalesweeper@v1.1.1
+        with:
+          repo-token: ${{ secrets.GH_BOT_TOKEN }}
+          message: >
+            It seems this discussion hasn't had any activity in the past 90 days.
+            To help keep our backlog tidy, we'll be closing this discussion.
+            If it's still something you'd like addressed, please let us know by leaving a comment.
+            Thanks!
+          days-before-close: '90'
+          close-unanswered: 'true'
+          category: ${{ matrix.category }}
+          close-reason: 'OUTDATED'
+          # todo: dry-run default is true during testing
+          dry-run: ${{ github.event_name == 'schedule' && 'true' || github.event.inputs.dry-run }}