Add dependabot support (#223)

* Add dependabot support

Several github actions used by workflows are out of date
and can be automatically checked by dependabot.

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>

* Only update github actions

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>

---------

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>

Author: dthaler

.github/dependabot.yml

@@ -0,0 +1,17 @@
+# Automatically opens PRs for dependency updates.
+# Can be turned on and off for org or repository via "Code security and analysis" tab .
+# See https://docs.github.com/en/code-security/dependabot/dependabot-alerts/configuring-dependabot-alerts
+version: 2
+updates:
+  # Updates GHA dependencies
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: monthly
+      time: "05:00"
+      timezone: America/Los_Angeles
+    groups:
+      actions:
+        patterns:
+          - "*"
+    open-pull-requests-limit: 3