add dependabot config

.github/dependabot.yml

@@ -0,0 +1,28 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+  - package-ecosystem: "npm" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "monthly"
+    ignore:
+      # chai is esmodule only.
+      - dependency-name: "chai"
+        versions: [">=5.0.0"]
+      # sinon-chai 4.x+ supports chai 5.x+.
+      - dependency-name: "sinon-chai"
+        versions: [">=4.0.0"]
+      # nyc is Node18+ only starting on nyc@16.x.
+      - dependency-name: "nyc"
+        versions: [">=16.0.0"]
+    groups:
+      development-dependencies:
+        dependency-type: "development"
+        applies-to: version-updates
+        update-types:
+        - "minor"
+        - "patch"