ci: add renovate auto-approve workflow

Calls the centralised reusable workflow in reqstool/.github to
auto-approve Renovate PRs, satisfying the required-review branch
protection rule and unblocking Renovate's auto-merge.

Signed-off-by: jimisola <jimisola@jimisola.com>

Author: Jimisola Laursen

.github/workflows/renovate-approve.yml

@@ -0,0 +1,11 @@
+name: Renovate auto-approve
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+
+jobs:
+  approve:
+    uses: reqstool/.github/.github/workflows/renovate-approve.yml@main