ci: add dependabot config file

Signed-off-by: umarcor <unai.martinezcorral@ehu.eus>

.github/dependabot.yml

diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..4ff3c23
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,16 @@
+version: 2
+updates:
+- package-ecosystem: gitsubmodule
+  directory: /
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 99
+  labels:
+  - dependencies
+  - kokoro:force-run
+  - third-party
+- package-ecosystem: github-actions
+  directory: /
+  schedule:
+    interval: weekly
+  open-pull-requests-limit: 99