Set up dependabot

This uses the same configuration as Memray is using.

Signed-off-by: Matt Wozniski <godlygeek@gmail.com>

Author: godlygeek

.github/dependabot.yml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    cooldown:
+      default-days: 7
+  - package-ecosystem: "docker"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    cooldown:
+      default-days: 7