add automatic updates via niv

.github/niv-updates.yml

@@ -0,0 +1,17 @@
+name: Automated niv-managed dependency updates
+on:
+  schedule:
+    # Every friday
+    - cron:  '0 0 * * FRI'
+jobs:
+  niv-updater:
+    name: 'Create PRs for niv-managed dependencies'
+    runs-on: ubuntu-latest
+    steps:
+      # notice there is no checkout step
+      - name: niv-updater-action
+        uses: knl/niv-updater-action@v5
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          pull_request_base: 'develop'