Add dependabot config (#1654)

Signed-off-by: Jari Kolehmainen <jari.kolehmainen@gmail.com>

.github/dependabot.yml

+# Please see the documentation for all configuration options:
+# https://help.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "npm" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "daily"