Add prerelease-1 suffix to version 6.0.0

Co-authored-by: petrinecp <5637849+petrinecp@users.noreply.github.com>

Author: Copilot

Directory.Build.props

@@ -6,7 +6,7 @@
     <Copyright>Copyright © $(Company) $([System.DateTime]::Now.Year)</Copyright>
     <Trademark>$(Company)™</Trademark>
     <VersionPrefix>6.0.0</VersionPrefix>
-    <VersionSuffix></VersionSuffix>
+    <VersionSuffix>prerelease-1</VersionSuffix>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
 
     <PackageProjectUrl>https://github.com/Kentico/xperience-by-kentico-tag-manager</PackageProjectUrl>