Update Dependabot schedule and add groups (#35)

Author: bartveneman

.github/dependabot.yml

@@ -6,8 +6,21 @@ updates:
   - package-ecosystem: 'npm'
     directory: '/'
     schedule:
-      interval: 'weekly'
+      interval: 'monthly'
+    groups:
+      vite:
+        patterns:
+          - 'vitest'
+          - '@vitest/*'
+      oxc:
+        patterns:
+          - 'oxlint'
+          - 'oxfmt'
   - package-ecosystem: 'github-actions'
     directory: '/'
     schedule:
-      interval: 'weekly'
+      interval: 'monthly'
+    groups:
+      github-actions:
+        patterns:
+          - '*'