.github/dependabot.yml: introduce scanning for obsolete GHA versions

Signed-off-by: Jim Klimov <jimklimov+nut@gmail.com>

Author: jimklimov

.github/dependabot.yml

@@ -0,0 +1,12 @@
+# 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
+# https://docs.github.com/en/code-security/how-tos/secure-your-supply-chain/secure-your-dependencies/keeping-your-actions-up-to-date-with-dependabot
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"