feat: add Dependabot config file

Set for GitHub Actions to check for update everyday.

When you add or update the dependabot.yml file, this triggers an immediate check for version updates. Any options that also affect security updates are used the next time a security alert triggers a pull request for a security update.

https://docs.github.com/en/github/administering-a-repository/configuration-options-for-dependency-updates

.github/dependabot.yml

+# Basic set up
+
+version: 2
+updates:
+
+  # Maintain dependencies for GitHub Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"