Configure Dependabot.

Change-Id: I7eccedf2aaa5d7e88e42466f3fa86845e26c6814
Signed-off-by: Andrew Walbran <qwandor@google.com>
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..98e44ee
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,10 @@
+version: 2
+updates:
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"