Create Dependabot config file (#82)

* Create Dependabot config file

* Update dependabot.yml

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Masafumi Koba <[email protected]>

Author: dependabot-preview[bot]

.github/dependabot.yml

@@ -0,0 +1,10 @@
+version: 2
+updates:
+  - package-ecosystem: npm
+    directory: "/"
+    schedule:
+      interval: monthly
+    open-pull-requests-limit: 5
+    versioning-strategy: widen
+    labels:
+      - "pr: dependencies"