Add ef-core dependabot group to combine EF NuGet and dotnet-ef tool updates

Agent-Logs-Url: https://github.com/IntelliTect/EssentialCSharp.Web/sessions/3e6a4e78-2c56-464a-a1b2-6a5bf1d2d3b9

Co-authored-by: BenjaminMichaelis <22186029+BenjaminMichaelis@users.noreply.github.com>

Author: Copilot

.github/dependabot.yml

@@ -26,6 +26,11 @@ updates:
           patterns:
             - "ContentFeedNuget"
             - "EssentialCSharp.Shared.Models"
+       ef-core:
+          applies-to: version-updates
+          patterns:
+            - "Microsoft.EntityFrameworkCore*"
+            - "dotnet-ef"
 
   - package-ecosystem: "github-actions" # See documentation for possible values
     directory: "/" # Location of package manifests