Migrate stale bot to github actions (#97)

.github/stale.yml

@@ -1,13 +0,0 @@
-# Number of days of inactivity before an Issue or Pull Request becomes stale
-daysUntilStale: 182
-
-# Label to use when marking as stale
-staleLabel: stale
-
-# 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. It will be closed if no further activity occurs.
-
-# Limit to only `issues` or `pulls`
-only: issues

.github/workflows/stale.yml

@@ -0,0 +1,19 @@
+name: Mark stale issues
+
+on:
+  schedule:
+  - cron: "0 0 * * *"
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/stale@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        days-before-stale: 182
+        stale-issue-label: stale
+        stale-issue-message: >
+          This issue has been automatically marked as stale because it has not had
+          recent activity. It will be closed if no further activity occurs.