Add net48 support

Author: lukespragg

src/Oxide.CSharp.csproj

@@ -12,7 +12,7 @@
     <PackageIconUrl>icon.png</PackageIconUrl>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>$(RepositoryUrl)</PackageProjectUrl>
-    <TargetFrameworks>net35;net40;net45;net46;netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net35;net40;net45;net46;net48;netstandard2.0;netstandard2.1</TargetFrameworks>
     <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
     <NoWarn>NU1701</NoWarn>
   </PropertyGroup>