Use full name as Author, since Owner is already kzu

The Author is a non-clickable text-only metadata field displayed on nuget.org. 
The Owner is the clickable identity, which points to kzu (and potentially other owners, like Devlooped and clarius).

Therefore, make it easily discoverable who's behind the package as a main author :)

Author: kzu

src/Directory.Build.props

@@ -19,7 +19,7 @@
   </PropertyGroup>
 
   <PropertyGroup Label="NuGet">
-    <Authors>kzu</Authors>
+    <Authors>Daniel Cazzulino</Authors>
     <Copyright>Copyright (C) Daniel Cazzulino and Contributors. All rights reserved.</Copyright>
     <PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>