Add Dependabot group configuration for Microsoft.Build.* dependencies

Co-authored-by: radical <[email protected]>

Author: Copilot

.github/dependabot.yml

@@ -9,3 +9,7 @@ updates:
     directory: "/src/SourceBrowser/" # Location of package manifests
     schedule:
       interval: "weekly"
+    groups:
+      microsoft-build-deps:
+        patterns:
+          - "Microsoft.Build.*"