[buildbot] CI: add dependabot scan

[LEDE Commits]

ynezz pushed a commit to buildbot.git, branch main:
https://git.openwrt.org/a898d87b7995b15b35d4db7511ae5372b98cf63f

commit a898d87b7995b15b35d4db7511ae5372b98cf63f
Author: Christian Marangi <ansuelsmth at gmail.com>
AuthorDate: Fri Apr 12 15:16:53 2024 +0200

    CI: add dependabot scan
    
    Add dependabot scan to warn and propose updates to our github actions.
    
    Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
---
 .github/dependabot.yml | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..41039d6
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,15 @@
+# Set update schedule for GitHub Actions
+
+version: 2
+updates:
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      # Check for updates to GitHub Actions every week
+      interval: "weekly"
+    # Prefix all commit messages with "CI" plus its scope, that is, a
+    # list of updated dependencies
+    commit-message:
+      prefix: "CI"
+      include: "scope"