chore(dependabot): Include GitHub Actions in Dependabot config (#7013)

## Explanation

This adds `actions/*` and `MetaMask/*` to the Dependabot config,
ensuring we keep these actions up to date as well. I've limited it to
these two, since we do use some other actions which are usually pinned
to a specific hash, and require explicit approval to be used first.

## References

MetaMask/metamask-module-template#274

## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [ ] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds Dependabot config for GitHub Actions with daily 06:00 runs on
main, allowing MetaMask/* and actions/*, and capping open PRs at 10.
> 
> - **Dependabot configuration**:
> - **GitHub Actions updates**: Add `package-ecosystem: github-actions`
with daily schedule at `06:00`, targeting `main`.
>     - Allow only `MetaMask/*` and `actions/*`.
>     - Set `open-pull-requests-limit` to `10`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
92188fd. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: Mrtenz

.github/dependabot.yml

@@ -1,5 +1,5 @@
 # Please see the documentation for all configuration options:
-# https://help.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
 
 version: 2
 updates:
@@ -10,3 +10,14 @@ updates:
     allow:
       - dependency-name: '@metamask/*'
     versioning-strategy: 'increase'
+
+  - package-ecosystem: 'github-actions'
+    directory: '/'
+    schedule:
+      interval: 'daily'
+      time: '06:00'
+    allow:
+      - dependency-name: 'MetaMask/*'
+      - dependency-name: 'actions/*'
+    target-branch: 'main'
+    open-pull-requests-limit: 10