chore: add stale bot for issue and PR hygiene (#2772)

Signed-off-by: Miguel Martinez <miguel@chainloop.dev>

Author: migmartri

.github/workflows/stale.yml

@@ -0,0 +1,30 @@
+name: Close inactive issues and pull requests
+
+on:
+  schedule:
+    - cron: '30 1 * * *'
+  workflow_dispatch:
+
+jobs:
+  close-issues:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/stale@3a9db7e6a41a89f618792c92c0e97cc736e1b13f # v10.0.0
+        with:
+          stale-issue-message: >
+            This issue is stale because it has been open for 60 days with no activity.
+            It will be closed in 7 days if no further activity occurs.
+          close-issue-message: >
+            This issue was closed because it has been inactive for 7 days since being marked as stale.
+            Feel free to reopen if it is still relevant.
+          stale-pr-message: >
+            This pull request is stale because it has been open for 60 days with no activity.
+            It will be closed in 7 days if no further activity occurs.
+          close-pr-message: >
+            This pull request was closed because it has been inactive for 7 days since being marked as stale.
+            Feel free to reopen if it is still relevant.
+          exempt-issue-labels: pinned,security
+          exempt-pr-labels: pinned,security