Add dependabot to the repository…

… and set it to update github actions.

Signed-off-by: Vincent Demeester <[email protected]>

.github/dependabot.yaml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"