ci: add Dependabot configuration

Enable Dependabot version updates for the applicable ecosystems
(github-actions, docker, and pip where present), mirroring the
configuration used in tutor core, so dependencies stay current.

Part of overhangio/tutor#1398

Author: Abdul-Muqadim-Arbisoft

.github/dependabot.yml

@@ -0,0 +1,25 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+
+  - package-ecosystem: "docker"
+    directory: "/tutorjupyter/templates/jupyter/build/hub"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+
+  - package-ecosystem: "docker"
+    directory: "/tutorjupyter/templates/jupyter/build/lab"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"