Enable dependabot to update actions (#420)

* Create dependabot.yml
* Only update major versions for Github Actions

Signed-off-by: Joyce <joycebrum@google.com>
Signed-off-by: Joe Richey <joerichey@google.com>
Co-authored-by: Joe Richey <joerichey@google.com>

Author: joycebrum

.github/dependabot.yml

@@ -0,0 +1,10 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+    ignore:
+      - dependency-name: "*"
+        update-types:
+          ["version-update:semver-minor", "version-update:semver-patch"]