chore: add Dependabot configuration for npm and GitHub Actions (#2)

Track the root npm toolchain and the CI GitHub Actions for updates.
Weekly schedule; minor+patch bumps grouped per ecosystem, majors get
individual PRs. PR titles use chore(deps)/chore(deps-dev) prefixes to
satisfy the Conventional Commit rule.

Signed-off-by: Thomas Müller <1005065+DeepDiver1975@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: DeepDiver1975

.github/dependabot.yml

@@ -0,0 +1,38 @@
+# Dependabot configuration.
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+#
+# Two ecosystems are tracked: the root npm toolchain (antora/asciidoctor/pagefind)
+# and the GitHub Actions pinned in .github/workflows/. PR titles use Conventional
+# Commit prefixes to satisfy the repo's semantic-commit rule. Minor + patch bumps
+# are grouped into a single PR per ecosystem; majors get individual PRs for review.
+version: 2
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: "chore(deps)"
+      prefix-development: "chore(deps-dev)"
+      include: "scope"
+    groups:
+      npm-minor-patch:
+        update-types:
+          - "minor"
+          - "patch"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    commit-message:
+      prefix: "chore(deps)"
+      include: "scope"
+    groups:
+      actions-minor-patch:
+        update-types:
+          - "minor"
+          - "patch"