ci: configure dependabot to monitor update for GitHub Actions

Part of #38

[skip ci]

.github/dependabot.yml

@@ -0,0 +1,26 @@
+# See for details:
+# - https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuring-dependabot-version-updates
+# - https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+version: 2
+updates:
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    # https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#allow
+    allow:
+      - dependency-name: "actions/checkout"
+      - dependency-name: "actions/setup-node"
+      - dependency-name: "actions/upload-artifact"
+    # https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#scheduleinterval
+    schedule:
+      interval: "daily"
+      time: "06:00"
+      timezone: "Asia/Novosibirsk"
+    # https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#commit-message
+    commit-message:
+      prefix: "ci"
+    assignees: [ "php-coder" ]
+    reviewers: [ "php-coder" ]
+    labels: [ "kind/dependency-update", "area/ci" ]
+    # https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#open-pull-requests-limit
+    open-pull-requests-limit: 1