feat: added workflow for auto-updating PRs

Author: mfranzke

.github/workflows/update-prs.yml

@@ -0,0 +1,24 @@
+---
+name: Update all PR branches if main gets update
+
+on:
+  push:
+    branches:
+      - "main"
+
+jobs:
+  update-prs:
+    name: Update PRs
+    runs-on: ubuntu-latest
+    steps:
+      - name: ⬇ Checkout repo
+        uses: actions/checkout@v3
+
+      - name: ⌚ Update PRs
+        id: cleanup
+        uses: actions/github-script@v6
+        with:
+          script: |
+            const { default: updatePrs } = await import('${{ github.workspace }}/.github/scripts/update-prs.js');
+            // print how many PRs are updated
+            console.log(await updatePrs({github, context}));