fix(ci): dependabot.yml (#110)

### Briefly, what does this PR introduce?
Dependabot for github-actions version upgrades.

Author: wdconinc

.github/dependabot.yml

@@ -0,0 +1,11 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"

.github/workflows/linux-eic-shell.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: cvmfs-contrib/github-action-cvmfs@v4
+    - uses: cvmfs-contrib/github-action-cvmfs@v5
     - uses: eic/run-cvmfs-osg-eic-shell@main
       with:
         platform-release: "eic_xl:nightly"