Add workflow to test rust-bitcoin-maintainer-tools update-stable action

Author: nyonson

.github/workflows/update-stable.yml

@@ -0,0 +1,24 @@
+name: Update Stable Toolchain
+
+on:
+  # Manual trigger for testing
+  workflow_dispatch:
+  # Uncomment to run automatically weekly
+  # schedule:
+  #   - cron: '5 0 * * 6'  # Weekly on Saturday at 00:05 UTC
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  update-stable:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Update stable version
+        uses: rust-bitcoin/rust-bitcoin-maintainer-tools/.github/actions/update-stable@master
+        with:
+          token: ${{ secrets.YONSON_TOKEN }}

stable-version

@@ -0,0 +1 @@
+1.84.0