Instruct Dependabot to run monthly

Instruct Dependabot to run monthly instead of daily.

Author: asbjornu

.github/dependabot.yml

@@ -3,25 +3,25 @@ updates:
 - package-ecosystem: nuget
   directory: "/"
   schedule:
-    interval: daily
+    interval: monthly
   target-branch: main
 
 - package-ecosystem: nuget
   directory: "/"
   schedule:
-    interval: daily
+    interval: monthly
   target-branch: support/1.x
   ignore:
   - dependency-name: Newtonsoft.Json
 
 - package-ecosystem: github-actions
   directory: "/"
   schedule:
-    interval: daily
+    interval: monthly
   target-branch: main
 
 - package-ecosystem: github-actions
   directory: "/"
   schedule:
-    interval: daily
+    interval: monthly
   target-branch: support/1.x