chore: Pin GitHub actions to a digest to follow best practices (#955)

Updates our renovate configuration which automates updating the actions.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Enables Renovate helper to pin GitHub Actions to immutable digests.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
191ef90. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: jsonbailey

renovate.json

@@ -1,5 +1,5 @@
 {
-  "extends": ["config:recommended"],
+  "extends": ["config:recommended", "helpers:pinGitHubActionDigests"],
   "packageRules": [
     {
       "enabled": false,