Enable NuGet Audit for security vulnerability scanning

Co-authored-by: marcpopMSFT <12663534+marcpopMSFT@users.noreply.github.com>

Author: Copilot

Directory.Build.props

@@ -39,6 +39,11 @@
 
     <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
     <CentralPackageTransitivePinningEnabled>true</CentralPackageTransitivePinningEnabled>
+
+    <!-- Enable NuGet Audit to check for security vulnerabilities -->
+    <NuGetAudit>true</NuGetAudit>
+    <NuGetAuditLevel>low</NuGetAuditLevel>
+    <NuGetAuditMode>all</NuGetAuditMode>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(IsTestProject)' == 'true'">